21620751 has 4 divisors (see below), whose sum is σ = 28827672. Its totient is φ = 14413832.

The previous prime is 21620749. The next prime is 21620789. The reversal of 21620751 is 15702612.

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 21620751 - 2¹ = 21620749 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21620791) 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, 3603456 + ... + 3603461.

It is an arithmetic number, because the mean of its divisors is an integer number (7206918).

Almost surely, 2^21620751 is an apocalyptic number.

21620751 is a deficient number, since it is larger than the sum of its proper divisors (7206921).

21620751 is an equidigital number, since it uses as much as digits as its factorization.

21620751 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7206920.

The product of its (nonzero) digits is 840, while the sum is 24.

The square root of 21620751 is about 4649.8119316807. The cubic root of 21620751 is about 278.5844844449.

The spelling of 21620751 in words is "twenty-one million, six hundred twenty thousand, seven hundred fifty-one".