21975779 has 8 divisors (see below), whose sum is σ = 25178208. Its totient is φ = 18789120.

The previous prime is 21975773. The next prime is 21975809. The reversal of 21975779 is 97757912.

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

It is not a de Polignac number, because 21975779 - 2⁴ = 21975763 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21975773) 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, 782 + ... + 6675.

It is an arithmetic number, because the mean of its divisors is an integer number (3147276).

Almost surely, 2^21975779 is an apocalyptic number.

21975779 is a deficient number, since it is larger than the sum of its proper divisors (3202429).

21975779 is an equidigital number, since it uses as much as digits as its factorization.

21975779 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7885.

The product of its digits is 277830, while the sum is 47.

The square root of 21975779 is about 4687.8330814994. The cubic root of 21975779 is about 280.1010647072.

The spelling of 21975779 in words is "twenty-one million, nine hundred seventy-five thousand, seven hundred seventy-nine".