21820751 has 2 divisors, whose sum is σ = 21820752. Its totient is φ = 21820750.

The previous prime is 21820709. The next prime is 21820769. The reversal of 21820751 is 15702812.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21820751 - 2²² = 17626447 is a prime.

It is a super-2 number, since 2×21820751² = 952290348408002, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21820751.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21820781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10910375 + 10910376.

It is an arithmetic number, because the mean of its divisors is an integer number (10910376).

Almost surely, 2^21820751 is an apocalyptic number.

21820751 is a deficient number, since it is larger than the sum of its proper divisors (1).

21820751 is an equidigital number, since it uses as much as digits as its factorization.

21820751 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1120, while the sum is 26.

The square root of 21820751 is about 4671.2686713569. The cubic root of 21820751 is about 279.4408526888.

The spelling of 21820751 in words is "twenty-one million, eight hundred twenty thousand, seven hundred fifty-one".