21399513 has 4 divisors (see below), whose sum is σ = 28532688. Its totient is φ = 14266340.

The previous prime is 21399503. The next prime is 21399527. The reversal of 21399513 is 31599312.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21399513 - 2¹⁷ = 21268441 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21399503) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3566583 + ... + 3566588.

It is an arithmetic number, because the mean of its divisors is an integer number (7133172).

Almost surely, 2^21399513 is an apocalyptic number.

It is an amenable number.

21399513 is a deficient number, since it is larger than the sum of its proper divisors (7133175).

21399513 is an equidigital number, since it uses as much as digits as its factorization.

21399513 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7133174.

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

The square root of 21399513 is about 4625.9607650736. The cubic root of 21399513 is about 277.6310038055.

It can be divided in two parts, 21399 and 513, that added together give a palindrome (21912).

The spelling of 21399513 in words is "twenty-one million, three hundred ninety-nine thousand, five hundred thirteen".