21977321 has 4 divisors (see below), whose sum is σ = 22242192. Its totient is φ = 21712452.

The previous prime is 21977317. The next prime is 21977327. The reversal of 21977321 is 12377912.

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 a cyclic number.

It is not a de Polignac number, because 21977321 - 2² = 21977317 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21977327) 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, 132311 + ... + 132476.

It is an arithmetic number, because the mean of its divisors is an integer number (5560548).

Almost surely, 2^21977321 is an apocalyptic number.

It is an amenable number.

21977321 is a deficient number, since it is larger than the sum of its proper divisors (264871).

21977321 is an equidigital number, since it uses as much as digits as its factorization.

21977321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 264870.

The product of its digits is 5292, while the sum is 32.

The square root of 21977321 is about 4687.9975469277. The cubic root of 21977321 is about 280.1076159462.

The spelling of 21977321 in words is "twenty-one million, nine hundred seventy-seven thousand, three hundred twenty-one".