21369639 has 4 divisors (see below), whose sum is σ = 28492856. Its totient is φ = 14246424.

The previous prime is 21369617. The next prime is 21369659. The reversal of 21369639 is 93696312.

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

It is not a de Polignac number, because 21369639 - 2⁷ = 21369511 is a prime.

It is a super-2 number, since 2×21369639² = 913322941980642, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21369597 and 21369606.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21369659) 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, 3561604 + ... + 3561609.

It is an arithmetic number, because the mean of its divisors is an integer number (7123214).

Almost surely, 2^21369639 is an apocalyptic number.

21369639 is a deficient number, since it is larger than the sum of its proper divisors (7123217).

21369639 is an equidigital number, since it uses as much as digits as its factorization.

21369639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7123216.

The product of its digits is 52488, while the sum is 39.

The square root of 21369639 is about 4622.7306865099. The cubic root of 21369639 is about 277.5017514702.

The spelling of 21369639 in words is "twenty-one million, three hundred sixty-nine thousand, six hundred thirty-nine".