21256909520 has 480 divisors, whose sum is σ = 65952921600. Its totient is φ = 6292070400.

The previous prime is 21256909501. The next prime is 21256909523. The reversal of 21256909520 is 2590965212.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21256909523) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 111292625 + ... + 111292815.

It is an arithmetic number, because the mean of its divisors is an integer number (137401920).

Almost surely, 2^21256909520 is an apocalyptic number.

21256909520 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 21256909520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32976460800).

21256909520 is an abundant number, since it is smaller than the sum of its proper divisors (44696012080).

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

21256909520 is a wasteful number, since it uses less digits than its factorization.

21256909520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 347 (or 334 counting only the distinct ones).

The product of its (nonzero) digits is 97200, while the sum is 41.

The spelling of 21256909520 in words is "twenty-one billion, two hundred fifty-six million, nine hundred nine thousand, five hundred twenty".