21577908788 has 12 divisors (see below), whose sum is σ = 38781917412. Its totient is φ = 10497360960.

The previous prime is 21577908787. The next prime is 21577908797. The reversal of 21577908788 is 88780977512.

It can be written as a sum of positive squares in 2 ways, for example, as 15366577444 + 6211331344 = 123962^2 + 78812^2 .

It is a super-2 number, since 2×21577908788² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21577908788.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21577908787) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 72898193 + ... + 72898488.

It is an arithmetic number, because the mean of its divisors is an integer number (3231826451).

Almost surely, 2^21577908788 is an apocalyptic number.

It is an amenable number.

21577908788 is a deficient number, since it is larger than the sum of its proper divisors (17204008624).

21577908788 is a wasteful number, since it uses less digits than its factorization.

21577908788 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 145796722 (or 145796720 counting only the distinct ones).

The product of its (nonzero) digits is 15805440, while the sum is 62.

The spelling of 21577908788 in words is "twenty-one billion, five hundred seventy-seven million, nine hundred eight thousand, seven hundred eighty-eight".