21807139 has 4 divisors (see below), whose sum is σ = 21825720. Its totient is φ = 21788560.

The previous prime is 21807133. The next prime is 21807157. The reversal of 21807139 is 93170812.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21807139 is a prime.

It is a super-2 number, since 2×21807139² = 951102622730642, which contains 22 as substring.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21807139.

It is not an unprimeable number, because it can be changed into a prime (21807133) 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, 7402 + ... + 9919.

It is an arithmetic number, because the mean of its divisors is an integer number (5456430).

Almost surely, 2^21807139 is an apocalyptic number.

21807139 is a deficient number, since it is larger than the sum of its proper divisors (18581).

21807139 is a wasteful number, since it uses less digits than its factorization.

21807139 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18580.

The product of its (nonzero) digits is 3024, while the sum is 31.

The square root of 21807139 is about 4669.8114522965. The cubic root of 21807139 is about 279.3827346143.

The spelling of 21807139 in words is "twenty-one million, eight hundred seven thousand, one hundred thirty-nine".