21759623 has 2 divisors, whose sum is σ = 21759624. Its totient is φ = 21759622.

The previous prime is 21759601. The next prime is 21759629. The reversal of 21759623 is 32695712.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21759623 - 2¹² = 21755527 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21759629) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10879811 + 10879812.

It is an arithmetic number, because the mean of its divisors is an integer number (10879812).

Almost surely, 2^21759623 is an apocalyptic number.

21759623 is a deficient number, since it is larger than the sum of its proper divisors (1).

21759623 is an equidigital number, since it uses as much as digits as its factorization.

21759623 is an evil number, because the sum of its binary digits is even.

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

The square root of 21759623 is about 4664.7211063471. The cubic root of 21759623 is about 279.1796695609.

The spelling of 21759623 in words is "twenty-one million, seven hundred fifty-nine thousand, six hundred twenty-three".