21642289 has 2 divisors, whose sum is σ = 21642290. Its totient is φ = 21642288.

The previous prime is 21642281. The next prime is 21642307. The reversal of 21642289 is 98224612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14379264 + 7263025 = 3792^2 + 2695^2 .

It is a cyclic number.

It is not a de Polignac number, because 21642289 - 2³ = 21642281 is a prime.

It is not a weakly prime, because it can be changed into another prime (21642281) 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, 10821144 + 10821145.

It is an arithmetic number, because the mean of its divisors is an integer number (10821145).

Almost surely, 2^21642289 is an apocalyptic number.

It is an amenable number.

21642289 is a deficient number, since it is larger than the sum of its proper divisors (1).

21642289 is an equidigital number, since it uses as much as digits as its factorization.

21642289 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 13824, while the sum is 34.

The square root of 21642289 is about 4652.1273628309. The cubic root of 21642289 is about 278.6769598224.

The spelling of 21642289 in words is "twenty-one million, six hundred forty-two thousand, two hundred eighty-nine".