21939559 has 2 divisors, whose sum is σ = 21939560. Its totient is φ = 21939558.

The previous prime is 21939529. The next prime is 21939581. The reversal of 21939559 is 95593912.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21939559 - 2⁵ = 21939527 is a prime.

It is a super-2 number, since 2×21939559² = 962688498228962, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21939529) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10969779 + 10969780.

It is an arithmetic number, because the mean of its divisors is an integer number (10969780).

Almost surely, 2^21939559 is an apocalyptic number.

21939559 is a deficient number, since it is larger than the sum of its proper divisors (1).

21939559 is an equidigital number, since it uses as much as digits as its factorization.

21939559 is an evil number, because the sum of its binary digits is even.

The product of its digits is 109350, while the sum is 43.

The square root of 21939559 is about 4683.9682962206. The cubic root of 21939559 is about 279.9470945961.

The spelling of 21939559 in words is "twenty-one million, nine hundred thirty-nine thousand, five hundred fifty-nine".