21055579 has 2 divisors, whose sum is σ = 21055580. Its totient is φ = 21055578.

The previous prime is 21055561. The next prime is 21055583. The reversal of 21055579 is 97555012.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21055579 - 2⁷ = 21055451 is a prime.

It is not a weakly prime, because it can be changed into another prime (21055589) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10527789 + 10527790.

It is an arithmetic number, because the mean of its divisors is an integer number (10527790).

Almost surely, 2^21055579 is an apocalyptic number.

21055579 is a deficient number, since it is larger than the sum of its proper divisors (1).

21055579 is an equidigital number, since it uses as much as digits as its factorization.

21055579 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 15750, while the sum is 34.

The square root of 21055579 is about 4588.6358539331. The cubic root of 21055579 is about 276.1355972720.

The spelling of 21055579 in words is "twenty-one million, fifty-five thousand, five hundred seventy-nine".