21256917000 has 384 divisors, whose sum is σ = 75290342400. Its totient is φ = 4984320000.

The previous prime is 21256916999. The next prime is 21256917007. The reversal of 21256917000 is 71965212.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is not an unprimeable number, because it can be changed into a prime (21256917007) 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, 11252056 + ... + 11253944.

It is an arithmetic number, because the mean of its divisors is an integer number (196068600).

Almost surely, 2^21256917000 is an apocalyptic number.

21256917000 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 21256917000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37645171200).

21256917000 is an abundant number, since it is smaller than the sum of its proper divisors (54033425400).

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

21256917000 is a wasteful number, since it uses less digits than its factorization.

21256917000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1966 (or 1941 counting only the distinct ones).

The product of its (nonzero) digits is 7560, while the sum is 33.

The spelling of 21256917000 in words is "twenty-one billion, two hundred fifty-six million, nine hundred seventeen thousand".