21976439 has 2 divisors, whose sum is σ = 21976440. Its totient is φ = 21976438.

The previous prime is 21976433. The next prime is 21976441. The reversal of 21976439 is 93467912.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21976439 is a prime.

It is a super-2 number, since 2×21976439² = 965927742241442, which contains 22 as substring.

Together with 21976441, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21976396 and 21976405.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21976433) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10988219 + 10988220.

It is an arithmetic number, because the mean of its divisors is an integer number (10988220).

Almost surely, 2^21976439 is an apocalyptic number.

21976439 is a deficient number, since it is larger than the sum of its proper divisors (1).

21976439 is an equidigital number, since it uses as much as digits as its factorization.

21976439 is an evil number, because the sum of its binary digits is even.

The product of its digits is 81648, while the sum is 41.

The square root of 21976439 is about 4687.9034759688. The cubic root of 21976439 is about 280.1038687770.

The spelling of 21976439 in words is "twenty-one million, nine hundred seventy-six thousand, four hundred thirty-nine".