21225521664 has 320 divisors, whose sum is σ = 66070414080. Its totient is φ = 6715146240.

The previous prime is 21225521663. The next prime is 21225521671. The reversal of 21225521664 is 46612552212.

21225521664 is a `hidden beast` number, since 2 + 122 + 5 + 521 + 6 + 6 + 4 = 666.

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

It is not an unprimeable number, because it can be changed into a prime (21225521663) 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, 76626294 + ... + 76626570.

It is an arithmetic number, because the mean of its divisors is an integer number (206470044).

Almost surely, 2^21225521664 is an apocalyptic number.

21225521664 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 21225521664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33035207040).

21225521664 is an abundant number, since it is smaller than the sum of its proper divisors (44844892416).

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

21225521664 is a wasteful number, since it uses less digits than its factorization.

21225521664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 568 (or 546 counting only the distinct ones).

The product of its digits is 57600, while the sum is 36.

The spelling of 21225521664 in words is "twenty-one billion, two hundred twenty-five million, five hundred twenty-one thousand, six hundred sixty-four".