21311977 has 8 divisors (see below), whose sum is σ = 22476800. Its totient is φ = 20151504.

The previous prime is 21311959. The next prime is 21311981. The reversal of 21311977 is 77911312.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21311977 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21311957) 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, 16024 + ... + 17302.

It is an arithmetic number, because the mean of its divisors is an integer number (2809600).

Almost surely, 2^21311977 is an apocalyptic number.

It is an amenable number.

21311977 is a deficient number, since it is larger than the sum of its proper divisors (1164823).

21311977 is a wasteful number, since it uses less digits than its factorization.

21311977 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2175.

The product of its digits is 2646, while the sum is 31.

The square root of 21311977 is about 4616.4896837316. The cubic root of 21311977 is about 277.2519309999.

The spelling of 21311977 in words is "twenty-one million, three hundred eleven thousand, nine hundred seventy-seven".