21959399 has 24 divisors (see below), whose sum is σ = 28169856. Its totient is φ = 16926000.

The previous prime is 21959341. The next prime is 21959407. The reversal of 21959399 is 99395912.

It is not a de Polignac number, because 21959399 - 2⁸ = 21959143 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21959339) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 70454 + ... + 70764.

It is an arithmetic number, because the mean of its divisors is an integer number (1173744).

Almost surely, 2^21959399 is an apocalyptic number.

21959399 is a deficient number, since it is larger than the sum of its proper divisors (6210457).

21959399 is a wasteful number, since it uses less digits than its factorization.

21959399 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 467 (or 460 counting only the distinct ones).

The product of its digits is 196830, while the sum is 47.

The square root of 21959399 is about 4686.0856799679. The cubic root of 21959399 is about 280.0314547996.

The spelling of 21959399 in words is "twenty-one million, nine hundred fifty-nine thousand, three hundred ninety-nine".