21949857 has 12 divisors (see below), whose sum is σ = 31746000. Its totient is φ = 14614488.

The previous prime is 21949853. The next prime is 21949867. The reversal of 21949857 is 75894912.

It is not a de Polignac number, because 21949857 - 2² = 21949853 is a prime.

It is a Smith number, since the sum of its digits (45) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (21949853) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 12678 + ... + 14304.

It is an arithmetic number, because the mean of its divisors is an integer number (2645500).

Almost surely, 2^21949857 is an apocalyptic number.

It is an amenable number.

21949857 is a deficient number, since it is larger than the sum of its proper divisors (9796143).

21949857 is a wasteful number, since it uses less digits than its factorization.

21949857 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3132 (or 3129 counting only the distinct ones).

The product of its digits is 181440, while the sum is 45.

The square root of 21949857 is about 4685.0674488208. The cubic root of 21949857 is about 279.9908883089.

The spelling of 21949857 in words is "twenty-one million, nine hundred forty-nine thousand, eight hundred fifty-seven".