21731657328 has 120 divisors (see below), whose sum is σ = 65278687968. Its totient is φ = 6724325376.

The previous prime is 21731657317. The next prime is 21731657369. The reversal of 21731657328 is 82375613712.

21731657328 is a `hidden beast` number, since 2 + 1 + 7 + 316 + 5 + 7 + 328 = 666.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 117901 + ... + 239507.

Almost surely, 2^21731657328 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 21731657328, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32639343984).

21731657328 is an abundant number, since it is smaller than the sum of its proper divisors (43547030640).

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

21731657328 is a wasteful number, since it uses less digits than its factorization.

21731657328 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 121711 (or 121702 counting only the distinct ones).

The product of its digits is 423360, while the sum is 45.

The spelling of 21731657328 in words is "twenty-one billion, seven hundred thirty-one million, six hundred fifty-seven thousand, three hundred twenty-eight".