21121533657 has 48 divisors (see below), whose sum is σ = 36344394112. Its totient is φ = 11567888640.

The previous prime is 21121533541. The next prime is 21121533661. The reversal of 21121533657 is 75633512112.

21121533657 is a `hidden beast` number, since 2 + 112 + 1 + 533 + 6 + 5 + 7 = 666.

It is not a de Polignac number, because 21121533657 - 2⁷ = 21121533529 is a prime.

It is a super-2 number, since 2×21121533657² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21121533157) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 88557 + ... + 223797.

Almost surely, 2^21121533657 is an apocalyptic number.

It is an amenable number.

21121533657 is a deficient number, since it is larger than the sum of its proper divisors (15222860455).

21121533657 is a wasteful number, since it uses less digits than its factorization.

21121533657 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 135358 (or 135355 counting only the distinct ones).

The product of its digits is 37800, while the sum is 36.

The spelling of 21121533657 in words is "twenty-one billion, one hundred twenty-one million, five hundred thirty-three thousand, six hundred fifty-seven".