21620745 has 12 divisors (see below), whose sum is σ = 37476036. Its totient is φ = 11531040.

The previous prime is 21620737. The next prime is 21620749. The reversal of 21620745 is 54702612.

It can be written as a sum of positive squares in 2 ways, for example, as 14379264 + 7241481 = 3792^2 + 2691^2 .

It is not a de Polignac number, because 21620745 - 2³ = 21620737 is a prime.

It is a super-2 number, since 2×21620745² = 934913228710050, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21620749) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 240186 + ... + 240275.

It is an arithmetic number, because the mean of its divisors is an integer number (3123003).

Almost surely, 2^21620745 is an apocalyptic number.

It is an amenable number.

21620745 is a deficient number, since it is larger than the sum of its proper divisors (15855291).

21620745 is a wasteful number, since it uses less digits than its factorization.

21620745 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 480472 (or 480469 counting only the distinct ones).

The product of its (nonzero) digits is 3360, while the sum is 27.

The square root of 21620745 is about 4649.8112864932. The cubic root of 21620745 is about 278.5844586748.

The spelling of 21620745 in words is "twenty-one million, six hundred twenty thousand, seven hundred forty-five".