21642259 has 2 divisors, whose sum is σ = 21642260. Its totient is φ = 21642258.

The previous prime is 21642239. The next prime is 21642281. The reversal of 21642259 is 95224612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21642259 - 2⁹ = 21641747 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21642259.

It is not a weakly prime, because it can be changed into another prime (21642239) 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, 10821129 + 10821130.

It is an arithmetic number, because the mean of its divisors is an integer number (10821130).

Almost surely, 2^21642259 is an apocalyptic number.

21642259 is a deficient number, since it is larger than the sum of its proper divisors (1).

21642259 is an equidigital number, since it uses as much as digits as its factorization.

21642259 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 8640, while the sum is 31.

The square root of 21642259 is about 4652.1241384985. The cubic root of 21642259 is about 278.6768310574.

The spelling of 21642259 in words is "twenty-one million, six hundred forty-two thousand, two hundred fifty-nine".