21145697664 has 256 divisors, whose sum is σ = 72770880000. Its totient is φ = 5283201024.

The previous prime is 21145697663. The next prime is 21145697689. The reversal of 21145697664 is 46679654112.

It is a happy number.

It is a hoax number, since the sum of its digits (51) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21145697663) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 648012 + ... + 679860.

It is an arithmetic number, because the mean of its divisors is an integer number (284261250).

Almost surely, 2^21145697664 is an apocalyptic number.

21145697664 is a gapful number since it is divisible by the number (24) 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 21145697664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36385440000).

21145697664 is an abundant number, since it is smaller than the sum of its proper divisors (51625182336).

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

21145697664 is a wasteful number, since it uses less digits than its factorization.

21145697664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31905 (or 31893 counting only the distinct ones).

The product of its digits is 2177280, while the sum is 51.

The spelling of 21145697664 in words is "twenty-one billion, one hundred forty-five million, six hundred ninety-seven thousand, six hundred sixty-four".