21812805 has 24 divisors (see below), whose sum is σ = 43210752. Its totient is φ = 9971424.

The previous prime is 21812789. The next prime is 21812821. The reversal of 21812805 is 50821812.

It is an interprime number because it is at equal distance from previous prime (21812789) and next prime (21812821).

It is not a de Polignac number, because 21812805 - 2⁴ = 21812789 is a prime.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 34309 + ... + 34938.

It is an arithmetic number, because the mean of its divisors is an integer number (1800448).

Almost surely, 2^21812805 is an apocalyptic number.

It is an amenable number.

21812805 is a deficient number, since it is larger than the sum of its proper divisors (21397947).

21812805 is a wasteful number, since it uses less digits than its factorization.

21812805 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 69265 (or 69262 counting only the distinct ones).

The product of its (nonzero) digits is 1280, while the sum is 27.

The square root of 21812805 is about 4670.4180755046. The cubic root of 21812805 is about 279.4069292216.

The spelling of 21812805 in words is "twenty-one million, eight hundred twelve thousand, eight hundred five".