21723659 has 2 divisors, whose sum is σ = 21723660. Its totient is φ = 21723658.

The previous prime is 21723649. The next prime is 21723701. The reversal of 21723659 is 95632712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21723659 - 2¹² = 21719563 is a prime.

It is not a weakly prime, because it can be changed into another prime (21723649) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10861829 + 10861830.

It is an arithmetic number, because the mean of its divisors is an integer number (10861830).

Almost surely, 2^21723659 is an apocalyptic number.

21723659 is a deficient number, since it is larger than the sum of its proper divisors (1).

21723659 is an equidigital number, since it uses as much as digits as its factorization.

21723659 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 22680, while the sum is 35.

The square root of 21723659 is about 4660.8646193598. The cubic root of 21723659 is about 279.0257766638.

The spelling of 21723659 in words is "twenty-one million, seven hundred twenty-three thousand, six hundred fifty-nine".