21243997829880 has 768 divisors, whose sum is σ = 87955391462400. Its totient is φ = 4536624153600.

The previous prime is 21243997829863. The next prime is 21243997829881. The reversal of 21243997829880 is 8892879934212.

21243997829880 is a `hidden beast` number, since 2 + 1 + 2 + 4 + 399 + 78 + 2 + 98 + 80 = 666.

It is a super-2 number, since 2×21243997829880² (a number of 27 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (72).

It is a junction number, because it is equal to n+sod(n) for n = 21243997829799 and 21243997829808.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21243997829881) by changing a digit.

It is a polite number, since it can be written in 191 ways as a sum of consecutive naturals, for example, 52134930 + ... + 52540830.

It is an arithmetic number, because the mean of its divisors is an integer number (114525249300).

Almost surely, 2^{21243997829880} is an apocalyptic number.

21243997829880 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21243997829880, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (43977695731200).

21243997829880 is an abundant number, since it is smaller than the sum of its proper divisors (66711393632520).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21243997829880 is a wasteful number, since it uses less digits than its factorization.

21243997829880 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 406001 (or 405984 counting only the distinct ones).

The product of its (nonzero) digits is 250822656, while the sum is 72.

The spelling of 21243997829880 in words is "twenty-one trillion, two hundred forty-three billion, nine hundred ninety-seven million, eight hundred twenty-nine thousand, eight hundred eighty".