21392971 has 2 divisors, whose sum is σ = 21392972. Its totient is φ = 21392970.

The previous prime is 21392947. The next prime is 21392989. The reversal of 21392971 is 17929312.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21392971 - 2⁷ = 21392843 is a prime.

It is not a weakly prime, because it can be changed into another prime (21392071) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10696485 + 10696486.

It is an arithmetic number, because the mean of its divisors is an integer number (10696486).

Almost surely, 2^21392971 is an apocalyptic number.

21392971 is a deficient number, since it is larger than the sum of its proper divisors (1).

21392971 is an equidigital number, since it uses as much as digits as its factorization.

21392971 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6804, while the sum is 34.

The square root of 21392971 is about 4625.2536146681. The cubic root of 21392971 is about 277.6027095924.

The spelling of 21392971 in words is "twenty-one million, three hundred ninety-two thousand, nine hundred seventy-one".