21231979 has 2 divisors, whose sum is σ = 21231980. Its totient is φ = 21231978.

The previous prime is 21231971. The next prime is 21232007. The reversal of 21231979 is 97913212.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21231979 - 2³ = 21231971 is a prime.

It is not a weakly prime, because it can be changed into another prime (21231971) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10615989 + 10615990.

It is an arithmetic number, because the mean of its divisors is an integer number (10615990).

Almost surely, 2^21231979 is an apocalyptic number.

21231979 is a deficient number, since it is larger than the sum of its proper divisors (1).

21231979 is an equidigital number, since it uses as much as digits as its factorization.

21231979 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 21231979 is about 4607.8171621713. The cubic root of 21231979 is about 276.9045925122.

The spelling of 21231979 in words is "twenty-one million, two hundred thirty-one thousand, nine hundred seventy-nine".