21868257 has 8 divisors (see below), whose sum is σ = 29387776. Its totient is φ = 14463792.

The previous prime is 21868247. The next prime is 21868289. The reversal of 21868257 is 75286812.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21868257 - 2⁴ = 21868241 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21868247) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 28318 + ... + 29079.

It is an arithmetic number, because the mean of its divisors is an integer number (3673472).

Almost surely, 2^21868257 is an apocalyptic number.

It is an amenable number.

21868257 is a deficient number, since it is larger than the sum of its proper divisors (7519519).

21868257 is a wasteful number, since it uses less digits than its factorization.

21868257 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 57527.

The product of its digits is 53760, while the sum is 39.

The square root of 21868257 is about 4676.3508208859. The cubic root of 21868257 is about 279.6434961118.

The spelling of 21868257 in words is "twenty-one million, eight hundred sixty-eight thousand, two hundred fifty-seven".