21068257 has 4 divisors (see below), whose sum is σ = 24078016. Its totient is φ = 18058500.

The previous prime is 21068249. The next prime is 21068263. The reversal of 21068257 is 75286012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21068257 - 2³ = 21068249 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21068227) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1504869 + ... + 1504882.

It is an arithmetic number, because the mean of its divisors is an integer number (6019504).

Almost surely, 2^21068257 is an apocalyptic number.

It is an amenable number.

21068257 is a deficient number, since it is larger than the sum of its proper divisors (3009759).

21068257 is an equidigital number, since it uses as much as digits as its factorization.

21068257 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3009758.

The product of its (nonzero) digits is 6720, while the sum is 31.

The square root of 21068257 is about 4590.0171023647. The cubic root of 21068257 is about 276.1910084720.

The spelling of 21068257 in words is "twenty-one million, sixty-eight thousand, two hundred fifty-seven".