21172869 has 24 divisors (see below), whose sum is σ = 31391360. Its totient is φ = 13747968.

The previous prime is 21172861. The next prime is 21172883. The reversal of 21172869 is 96827112.

It is not a de Polignac number, because 21172869 - 2³ = 21172861 is a prime.

It is a super-2 number, since 2×21172869² = 896580763382322, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21172861) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 68814 + ... + 69120.

Almost surely, 2^21172869 is an apocalyptic number.

It is an amenable number.

21172869 is a deficient number, since it is larger than the sum of its proper divisors (10218491).

21172869 is a wasteful number, since it uses less digits than its factorization.

21172869 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 489 (or 486 counting only the distinct ones).

The product of its digits is 12096, while the sum is 36.

The square root of 21172869 is about 4601.3985917327. The cubic root of 21172869 is about 276.6473854726.

The spelling of 21172869 in words is "twenty-one million, one hundred seventy-two thousand, eight hundred sixty-nine".