21100251420 has 288 divisors, whose sum is σ = 69905384640. Its totient is φ = 5131468800.

The previous prime is 21100251407. The next prime is 21100251577. The reversal of 21100251420 is 2415200112.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 21100251393 and 21100251402.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 13178620 + ... + 13180220.

It is an arithmetic number, because the mean of its divisors is an integer number (242727030).

Almost surely, 2^21100251420 is an apocalyptic number.

21100251420 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 21100251420, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34952692320).

21100251420 is an abundant number, since it is smaller than the sum of its proper divisors (48805133220).

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

21100251420 is a wasteful number, since it uses less digits than its factorization.

21100251420 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1765 (or 1760 counting only the distinct ones).

The product of its (nonzero) digits is 160, while the sum is 18.

Adding to 21100251420 its reverse (2415200112), we get a palindrome (23515451532).

The spelling of 21100251420 in words is "twenty-one billion, one hundred million, two hundred fifty-one thousand, four hundred twenty".