21812945 has 32 divisors (see below), whose sum is σ = 33281280. Its totient is φ = 13328640.

The previous prime is 21812939. The next prime is 21812951. The reversal of 21812945 is 54921812.

It is an interprime number because it is at equal distance from previous prime (21812939) and next prime (21812951).

It is not a de Polignac number, because 21812945 - 2⁶ = 21812881 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Curzon number.

It is an unprimeable number.

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 31 ways as a sum of consecutive naturals, for example, 19871 + ... + 20939.

It is an arithmetic number, because the mean of its divisors is an integer number (1040040).

Almost surely, 2^21812945 is an apocalyptic number.

It is an amenable number.

21812945 is a deficient number, since it is larger than the sum of its proper divisors (11468335).

21812945 is a wasteful number, since it uses less digits than its factorization.

21812945 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1145.

The product of its digits is 5760, while the sum is 32.

The square root of 21812945 is about 4670.4330634321. The cubic root of 21812945 is about 279.4075269880.

The spelling of 21812945 in words is "twenty-one million, eight hundred twelve thousand, nine hundred forty-five".