21365801 has 2 divisors, whose sum is σ = 21365802. Its totient is φ = 21365800.

The previous prime is 21365791. The next prime is 21365809. The reversal of 21365801 is 10856312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20693401 + 672400 = 4549^2 + 820^2 .

It is a cyclic number.

It is not a de Polignac number, because 21365801 - 2⁶ = 21365737 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 (21365809) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10682900 + 10682901.

It is an arithmetic number, because the mean of its divisors is an integer number (10682901).

Almost surely, 2^21365801 is an apocalyptic number.

It is an amenable number.

21365801 is a deficient number, since it is larger than the sum of its proper divisors (1).

21365801 is an equidigital number, since it uses as much as digits as its factorization.

21365801 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1440, while the sum is 26.

The square root of 21365801 is about 4622.3155452652. The cubic root of 21365801 is about 277.4851373151.

The spelling of 21365801 in words is "twenty-one million, three hundred sixty-five thousand, eight hundred one".