21051797400 has 192 divisors, whose sum is σ = 72595130400. Its totient is φ = 5607360000.

The previous prime is 21051797309. The next prime is 21051797407. The reversal of 21051797400 is 479715012.

It is a happy number.

21051797400 is a `hidden beast` number, since 2 + 10 + 517 + 97 + 40 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21051797407) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 6375750 + ... + 6379050.

Almost surely, 2^21051797400 is an apocalyptic number.

21051797400 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 21051797400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36297565200).

21051797400 is an abundant number, since it is smaller than the sum of its proper divisors (51543333000).

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

21051797400 is a wasteful number, since it uses less digits than its factorization.

21051797400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4507 (or 4492 counting only the distinct ones).

The product of its (nonzero) digits is 17640, while the sum is 36.

The spelling of 21051797400 in words is "twenty-one billion, fifty-one million, seven hundred ninety-seven thousand, four hundred".