21879899 has 2 divisors, whose sum is σ = 21879900. Its totient is φ = 21879898.

The previous prime is 21879883. The next prime is 21879917. The reversal of 21879899 is 99897812.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21879899 - 2⁴ = 21879883 is a prime.

It is a Sophie Germain prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21879899.

It is not a weakly prime, because it can be changed into another prime (21879499) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10939949 + 10939950.

It is an arithmetic number, because the mean of its divisors is an integer number (10939950).

Almost surely, 2^21879899 is an apocalyptic number.

21879899 is a deficient number, since it is larger than the sum of its proper divisors (1).

21879899 is an equidigital number, since it uses as much as digits as its factorization.

21879899 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 653184, while the sum is 53.

The square root of 21879899 is about 4677.5954292777. The cubic root of 21879899 is about 279.6931118939.

The spelling of 21879899 in words is "twenty-one million, eight hundred seventy-nine thousand, eight hundred ninety-nine".