21339971 has 2 divisors, whose sum is σ = 21339972. Its totient is φ = 21339970.

The previous prime is 21339961. The next prime is 21339977. The reversal of 21339971 is 17993312.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21339971 is a prime.

It is not a weakly prime, because it can be changed into another prime (21339977) 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, 10669985 + 10669986.

It is an arithmetic number, because the mean of its divisors is an integer number (10669986).

Almost surely, 2^21339971 is an apocalyptic number.

21339971 is a deficient number, since it is larger than the sum of its proper divisors (1).

21339971 is an equidigital number, since it uses as much as digits as its factorization.

21339971 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 10206, while the sum is 35.

The square root of 21339971 is about 4619.5206461277. The cubic root of 21339971 is about 277.3732711389.

The spelling of 21339971 in words is "twenty-one million, three hundred thirty-nine thousand, nine hundred seventy-one".