21108312369 has 21 divisors (see below), whose sum is σ = 31653873499. Its totient is φ = 14069593080.

The previous prime is 21108312347. The next prime is 21108312391. The reversal of 21108312369 is 96321380112.

The square root of 21108312369 is 145287.

It is a perfect power (a square), and thus also a powerful number.

21108312369 is a `hidden beast` number, since 211 + 0 + 83 + 1 + 2 + 369 = 666.

It is an interprime number because it is at equal distance from previous prime (21108312347) and next prime (21108312391).

It can be written as a sum of positive squares in only one way, i.e., 6866276769 + 14242035600 = 82863^2 + 119340^2 .

It is not a de Polignac number, because 21108312369 - 2³¹ = 18960828721 is a prime.

It is a super-2 number, since 2×21108312369² (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 (21108312469) by changing a digit.

It is a polite number, since it can be written in 20 ways as a sum of consecutive naturals, for example, 3920059 + ... + 3925439.

Almost surely, 2^21108312369 is an apocalyptic number.

21108312369 is the 145287-th square number.

21108312369 is the 72644-th centered octagonal number.

It is an amenable number.

21108312369 is a deficient number, since it is larger than the sum of its proper divisors (10545561130).

21108312369 is an frugal number, since it uses more digits than its factorization.

21108312369 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10780 (or 5384 counting only the distinct ones).

The product of its (nonzero) digits is 15552, while the sum is 36.

Multiplying 21108312369 by its sum of digits (36), we get a square (759899245284 = 871722²).

The spelling of 21108312369 in words is "twenty-one billion, one hundred eight million, three hundred twelve thousand, three hundred sixty-nine".