21311973 has 12 divisors (see below), whose sum is σ = 31777408. Its totient is φ = 13749480.

The previous prime is 21311959. The next prime is 21311981. The reversal of 21311973 is 37911312.

It is not a de Polignac number, because 21311973 - 2⁴ = 21311957 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21311903) 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, 37915 + ... + 38472.

Almost surely, 2^21311973 is an apocalyptic number.

It is an amenable number.

21311973 is a deficient number, since it is larger than the sum of its proper divisors (10465435).

21311973 is a wasteful number, since it uses less digits than its factorization.

21311973 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 76424 (or 76421 counting only the distinct ones).

The product of its digits is 1134, while the sum is 27.

The square root of 21311973 is about 4616.4892505019. The cubic root of 21311973 is about 277.2519136543.

The spelling of 21311973 in words is "twenty-one million, three hundred eleven thousand, nine hundred seventy-three".