21964591 has 4 divisors (see below), whose sum is σ = 23961384. Its totient is φ = 19967800.

The previous prime is 21964573. The next prime is 21964619. The reversal of 21964591 is 19546912.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21964591 - 2⁵ = 21964559 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21964591.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21964511) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 998380 + ... + 998401.

It is an arithmetic number, because the mean of its divisors is an integer number (5990346).

Almost surely, 2^21964591 is an apocalyptic number.

21964591 is a deficient number, since it is larger than the sum of its proper divisors (1996793).

21964591 is a wasteful number, since it uses less digits than its factorization.

21964591 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1996792.

The product of its digits is 19440, while the sum is 37.

The square root of 21964591 is about 4686.6396277077. The cubic root of 21964591 is about 280.0535229315.

The spelling of 21964591 in words is "twenty-one million, nine hundred sixty-four thousand, five hundred ninety-one".