21147557832 has 72 divisors (see below), whose sum is σ = 57699437250. Its totient is φ = 6997284864.

The previous prime is 21147557831. The next prime is 21147557843. The reversal of 21147557832 is 23875574112.

21147557832 is a `hidden beast` number, since 2 + 1 + 1 + 4 + 75 + 578 + 3 + 2 = 666.

It can be written as a sum of positive squares in 3 ways, for example, as 16518932676 + 4628625156 = 128526^2 + 68034^2 .

It is a tau number, because it is divible by the number of its divisors (72).

It is not an unprimeable number, because it can be changed into a prime (21147557831) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 1343544 + ... + 1359192.

Almost surely, 2^21147557832 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 21147557832, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28849718625).

21147557832 is an abundant number, since it is smaller than the sum of its proper divisors (36551879418).

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

21147557832 is a wasteful number, since it uses less digits than its factorization.

21147557832 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15935 (or 15791 counting only the distinct ones).

The product of its digits is 470400, while the sum is 45.

The spelling of 21147557832 in words is "twenty-one billion, one hundred forty-seven million, five hundred fifty-seven thousand, eight hundred thirty-two".