21690959 has 2 divisors, whose sum is σ = 21690960. Its totient is φ = 21690958.

The previous prime is 21690943. The next prime is 21690961. The reversal of 21690959 is 95909612.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21690959 - 2⁴ = 21690943 is a prime.

Together with 21690961, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21690919) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10845479 + 10845480.

It is an arithmetic number, because the mean of its divisors is an integer number (10845480).

Almost surely, 2^21690959 is an apocalyptic number.

21690959 is a deficient number, since it is larger than the sum of its proper divisors (1).

21690959 is an equidigital number, since it uses as much as digits as its factorization.

21690959 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 43740, while the sum is 41.

The square root of 21690959 is about 4657.3553654408. The cubic root of 21690959 is about 278.8857031947.

It can be divided in two parts, 2 and 1690959, that added together give a palindrome (1690961).

The spelling of 21690959 in words is "twenty-one million, six hundred ninety thousand, nine hundred fifty-nine".