21604071972 has 144 divisors (see below), whose sum is σ = 59308381440. Its totient is φ = 6102609408.

The previous prime is 21604071953. The next prime is 21604072013. The reversal of 21604071972 is 27917040612.

It is a self number, because there is not a number n which added to its sum of digits gives 21604071972.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 30047029 + ... + 30047747.

It is an arithmetic number, because the mean of its divisors is an integer number (411863760).

Almost surely, 2^21604071972 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21604071972, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29654190720).

21604071972 is an abundant number, since it is smaller than the sum of its proper divisors (37704309468).

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

21604071972 is a wasteful number, since it uses less digits than its factorization.

21604071972 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1250 (or 1241 counting only the distinct ones).

The product of its (nonzero) digits is 42336, while the sum is 39.

The spelling of 21604071972 in words is "twenty-one billion, six hundred four million, seventy-one thousand, nine hundred seventy-two".