21313857 has 4 divisors (see below), whose sum is σ = 28418480. Its totient is φ = 14209236.

The previous prime is 21313841. The next prime is 21313861. The reversal of 21313857 is 75831312.

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 not a de Polignac number, because 21313857 - 2⁴ = 21313841 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21313807) 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, 3552307 + ... + 3552312.

It is an arithmetic number, because the mean of its divisors is an integer number (7104620).

Almost surely, 2^21313857 is an apocalyptic number.

It is an amenable number.

21313857 is a deficient number, since it is larger than the sum of its proper divisors (7104623).

21313857 is an equidigital number, since it uses as much as digits as its factorization.

21313857 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7104622.

The product of its digits is 5040, while the sum is 30.

The square root of 21313857 is about 4616.6932971554. The cubic root of 21313857 is about 277.2600831969.

The spelling of 21313857 in words is "twenty-one million, three hundred thirteen thousand, eight hundred fifty-seven".