21566953 has 2 divisors, whose sum is σ = 21566954. Its totient is φ = 21566952.

The previous prime is 21566927. The next prime is 21566971. The reversal of 21566953 is 35966512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17614809 + 3952144 = 4197^2 + 1988^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21566953 is a prime.

It is not a weakly prime, because it can be changed into another prime (21566453) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10783476 + 10783477.

It is an arithmetic number, because the mean of its divisors is an integer number (10783477).

Almost surely, 2^21566953 is an apocalyptic number.

It is an amenable number.

21566953 is a deficient number, since it is larger than the sum of its proper divisors (1).

21566953 is an equidigital number, since it uses as much as digits as its factorization.

21566953 is an evil number, because the sum of its binary digits is even.

The product of its digits is 48600, while the sum is 37.

The square root of 21566953 is about 4644.0233634210. The cubic root of 21566953 is about 278.3532292023.

The spelling of 21566953 in words is "twenty-one million, five hundred sixty-six thousand, nine hundred fifty-three".