21368857 has 2 divisors, whose sum is σ = 21368858. Its totient is φ = 21368856.

The previous prime is 21368843. The next prime is 21368861. The reversal of 21368857 is 75886312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18071001 + 3297856 = 4251^2 + 1816^2 .

It is a cyclic number.

It is not a de Polignac number, because 21368857 - 2⁷ = 21368729 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21362857) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10684428 + 10684429.

It is an arithmetic number, because the mean of its divisors is an integer number (10684429).

Almost surely, 2^21368857 is an apocalyptic number.

It is an amenable number.

21368857 is a deficient number, since it is larger than the sum of its proper divisors (1).

21368857 is an equidigital number, since it uses as much as digits as its factorization.

21368857 is an evil number, because the sum of its binary digits is even.

The product of its digits is 80640, while the sum is 40.

The square root of 21368857 is about 4622.6461036943. The cubic root of 21368857 is about 277.4983664650.

The spelling of 21368857 in words is "twenty-one million, three hundred sixty-eight thousand, eight hundred fifty-seven".