21890651 has 2 divisors, whose sum is σ = 21890652. Its totient is φ = 21890650.

The previous prime is 21890647. The next prime is 21890677. The reversal of 21890651 is 15609812.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21890651 - 2² = 21890647 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21895651) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10945325 + 10945326.

It is an arithmetic number, because the mean of its divisors is an integer number (10945326).

Almost surely, 2^21890651 is an apocalyptic number.

21890651 is a deficient number, since it is larger than the sum of its proper divisors (1).

21890651 is an equidigital number, since it uses as much as digits as its factorization.

21890651 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4320, while the sum is 32.

The square root of 21890651 is about 4678.7445965772. The cubic root of 21890651 is about 279.7389190504.

The spelling of 21890651 in words is "twenty-one million, eight hundred ninety thousand, six hundred fifty-one".