21513399 has 4 divisors (see below), whose sum is σ = 28684536. Its totient is φ = 14342264.

The previous prime is 21513383. The next prime is 21513403. The reversal of 21513399 is 99331512.

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 21513399 - 2⁴ = 21513383 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21513329) 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 in 3 ways as a sum of consecutive naturals, for example, 3585564 + ... + 3585569.

It is an arithmetic number, because the mean of its divisors is an integer number (7171134).

Almost surely, 2^21513399 is an apocalyptic number.

21513399 is a deficient number, since it is larger than the sum of its proper divisors (7171137).

21513399 is an equidigital number, since it uses as much as digits as its factorization.

21513399 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7171136.

The product of its digits is 7290, while the sum is 33.

The square root of 21513399 is about 4638.2538740349. The cubic root of 21513399 is about 278.1226405388.

It can be divided in two parts, 21513 and 399, that added together give a palindrome (21912).

The spelling of 21513399 in words is "twenty-one million, five hundred thirteen thousand, three hundred ninety-nine".