21373591 has 2 divisors, whose sum is σ = 21373592. Its totient is φ = 21373590.

The previous prime is 21373589. The next prime is 21373657. The reversal of 21373591 is 19537312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21373591 - 2¹ = 21373589 is a prime.

Together with 21373589, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21373501) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10686795 + 10686796.

It is an arithmetic number, because the mean of its divisors is an integer number (10686796).

Almost surely, 2^21373591 is an apocalyptic number.

21373591 is a deficient number, since it is larger than the sum of its proper divisors (1).

21373591 is an equidigital number, since it uses as much as digits as its factorization.

21373591 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5670, while the sum is 31.

The square root of 21373591 is about 4623.1581197272. The cubic root of 21373591 is about 277.5188570364.

The spelling of 21373591 in words is "twenty-one million, three hundred seventy-three thousand, five hundred ninety-one".