21940857 has 6 divisors (see below), whose sum is σ = 31692362. Its totient is φ = 14627232.

The previous prime is 21940843. The next prime is 21940909. The reversal of 21940857 is 75804912.

It can be written as a sum of positive squares in only one way, i.e., 19927296 + 2013561 = 4464^2 + 1419^2 .

It is not a de Polignac number, because 21940857 - 2⁷ = 21940729 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21940817) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1218928 + ... + 1218945.

Almost surely, 2^21940857 is an apocalyptic number.

It is an amenable number.

21940857 is a deficient number, since it is larger than the sum of its proper divisors (9751505).

21940857 is a wasteful number, since it uses less digits than its factorization.

21940857 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2437879 (or 2437876 counting only the distinct ones).

The product of its (nonzero) digits is 20160, while the sum is 36.

The square root of 21940857 is about 4684.1068518982. The cubic root of 21940857 is about 279.9526152808.

The spelling of 21940857 in words is "twenty-one million, nine hundred forty thousand, eight hundred fifty-seven".