21972779 has 6 divisors (see below), whose sum is σ = 22121820. Its totient is φ = 21824616.

The previous prime is 21972763. The next prime is 21972803. The reversal of 21972779 is 97727912.

It is not a de Polignac number, because 21972779 - 2⁴ = 21972763 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21972079) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 52232 + ... + 52650.

It is an arithmetic number, because the mean of its divisors is an integer number (3686970).

Almost surely, 2^21972779 is an apocalyptic number.

21972779 is a deficient number, since it is larger than the sum of its proper divisors (149041).

21972779 is an frugal number, since it uses more digits than its factorization.

21972779 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 877 (or 648 counting only the distinct ones).

The product of its digits is 111132, while the sum is 44.

The square root of 21972779 is about 4687.5130933150. The cubic root of 21972779 is about 280.0883182280.

The spelling of 21972779 in words is "twenty-one million, nine hundred seventy-two thousand, seven hundred seventy-nine".