21812807 has 4 divisors (see below), whose sum is σ = 22170456. Its totient is φ = 21455160.

The previous prime is 21812789. The next prime is 21812821. The reversal of 21812807 is 70821812.

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

It is a cyclic number.

It is not a de Polignac number, because 21812807 - 2¹² = 21808711 is a prime.

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 21812807.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21812827) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 178733 + ... + 178854.

It is an arithmetic number, because the mean of its divisors is an integer number (5542614).

Almost surely, 2^21812807 is an apocalyptic number.

21812807 is a deficient number, since it is larger than the sum of its proper divisors (357649).

21812807 is an equidigital number, since it uses as much as digits as its factorization.

21812807 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 357648.

The product of its (nonzero) digits is 1792, while the sum is 29.

The square root of 21812807 is about 4670.4182896182. The cubic root of 21812807 is about 279.4069377612.

The spelling of 21812807 in words is "twenty-one million, eight hundred twelve thousand, eight hundred seven".