21569879 has 2 divisors, whose sum is σ = 21569880. Its totient is φ = 21569878.

The previous prime is 21569861. The next prime is 21569903. The reversal of 21569879 is 97896512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21569879 - 2⁸ = 21569623 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21539879) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10784939 + 10784940.

It is an arithmetic number, because the mean of its divisors is an integer number (10784940).

Almost surely, 2^21569879 is an apocalyptic number.

21569879 is a deficient number, since it is larger than the sum of its proper divisors (1).

21569879 is an equidigital number, since it uses as much as digits as its factorization.

21569879 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 272160, while the sum is 47.

The square root of 21569879 is about 4644.3383812982. The cubic root of 21569879 is about 278.3658167434.

The spelling of 21569879 in words is "twenty-one million, five hundred sixty-nine thousand, eight hundred seventy-nine".