21977591 has 2 divisors, whose sum is σ = 21977592. Its totient is φ = 21977590.

The previous prime is 21977567. The next prime is 21977609. The reversal of 21977591 is 19577912.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21977591 - 2¹⁰ = 21976567 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21977531) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10988795 + 10988796.

It is an arithmetic number, because the mean of its divisors is an integer number (10988796).

Almost surely, 2^21977591 is an apocalyptic number.

21977591 is a deficient number, since it is larger than the sum of its proper divisors (1).

21977591 is an equidigital number, since it uses as much as digits as its factorization.

21977591 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 39690, while the sum is 41.

The square root of 21977591 is about 4688.0263437826. The cubic root of 21977591 is about 280.1087630188.

The spelling of 21977591 in words is "twenty-one million, nine hundred seventy-seven thousand, five hundred ninety-one".