21655759 has 2 divisors, whose sum is σ = 21655760. Its totient is φ = 21655758.

The previous prime is 21655729. The next prime is 21655787. The reversal of 21655759 is 95755612.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21655759 - 2⁷ = 21655631 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21655709) 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, 10827879 + 10827880.

It is an arithmetic number, because the mean of its divisors is an integer number (10827880).

Almost surely, 2^21655759 is an apocalyptic number.

21655759 is a deficient number, since it is larger than the sum of its proper divisors (1).

21655759 is an equidigital number, since it uses as much as digits as its factorization.

21655759 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 94500, while the sum is 40.

The square root of 21655759 is about 4653.5748624042. The cubic root of 21655759 is about 278.7347633222.

The spelling of 21655759 in words is "twenty-one million, six hundred fifty-five thousand, seven hundred fifty-nine".