21566201 has 2 divisors, whose sum is σ = 21566202. Its totient is φ = 21566200.

The previous prime is 21566191. The next prime is 21566219. The reversal of 21566201 is 10266512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14622976 + 6943225 = 3824^2 + 2635^2 .

It is a cyclic number.

It is not a de Polignac number, because 21566201 - 2¹⁰ = 21565177 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (21566221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10783100 + 10783101.

It is an arithmetic number, because the mean of its divisors is an integer number (10783101).

Almost surely, 2^21566201 is an apocalyptic number.

It is an amenable number.

21566201 is a deficient number, since it is larger than the sum of its proper divisors (1).

21566201 is an equidigital number, since it uses as much as digits as its factorization.

21566201 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 720, while the sum is 23.

The square root of 21566201 is about 4643.9423984369. The cubic root of 21566201 is about 278.3499939430.

The spelling of 21566201 in words is "twenty-one million, five hundred sixty-six thousand, two hundred one".