21553165638 has 32 divisors (see below), whose sum is σ = 47910463200. Its totient is φ = 7182207648.

The previous prime is 21553165637. The next prime is 21553165639. The reversal of 21553165638 is 83656135512.

21553165638 is a `hidden beast` number, since 2 + 1 + 5 + 5 + 3 + 1 + 6 + 5 + 638 = 666.

It is an interprime number because it is at equal distance from previous prime (21553165637) and next prime (21553165639).

It is a junction number, because it is equal to n+sod(n) for n = 21553165593 and 21553165602.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21553165633) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 124120 + ... + 241892.

It is an arithmetic number, because the mean of its divisors is an integer number (1497201975).

Almost surely, 2^21553165638 is an apocalyptic number.

21553165638 is an abundant number, since it is smaller than the sum of its proper divisors (26357297562).

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

21553165638 is a wasteful number, since it uses less digits than its factorization.

21553165638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 121173 (or 121167 counting only the distinct ones).

The product of its digits is 648000, while the sum is 45.

The spelling of 21553165638 in words is "twenty-one billion, five hundred fifty-three million, one hundred sixty-five thousand, six hundred thirty-eight".