21977689 has 4 divisors (see below), whose sum is σ = 22035456. Its totient is φ = 21919924.

The previous prime is 21977671. The next prime is 21977713. The reversal of 21977689 is 98677912.

It is a happy number.

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 21977689 - 2⁹ = 21977177 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21977609) 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, 28309 + ... + 29074.

It is an arithmetic number, because the mean of its divisors is an integer number (5508864).

Almost surely, 2^21977689 is an apocalyptic number.

It is an amenable number.

21977689 is a deficient number, since it is larger than the sum of its proper divisors (57767).

21977689 is an equidigital number, since it uses as much as digits as its factorization.

21977689 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 57766.

The product of its digits is 381024, while the sum is 49.

The square root of 21977689 is about 4688.0367959307. The cubic root of 21977689 is about 280.1091793613.

The spelling of 21977689 in words is "twenty-one million, nine hundred seventy-seven thousand, six hundred eighty-nine".