21977609 has 2 divisors, whose sum is σ = 21977610. Its totient is φ = 21977608.

The previous prime is 21977591. The next prime is 21977633. The reversal of 21977609 is 90677912.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16024009 + 5953600 = 4003^2 + 2440^2 .

It is a cyclic number.

It is not a de Polignac number, because 21977609 - 2²⁰ = 20929033 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21977639) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10988804 + 10988805.

It is an arithmetic number, because the mean of its divisors is an integer number (10988805).

Almost surely, 2^21977609 is an apocalyptic number.

It is an amenable number.

21977609 is a deficient number, since it is larger than the sum of its proper divisors (1).

21977609 is an equidigital number, since it uses as much as digits as its factorization.

21977609 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 47628, while the sum is 41.

The square root of 21977609 is about 4688.0282635667. The cubic root of 21977609 is about 280.1088394900.

The spelling of 21977609 in words is "twenty-one million, nine hundred seventy-seven thousand, six hundred nine".