21037613 has 4 divisors (see below), whose sum is σ = 21125148. Its totient is φ = 20950080.

The previous prime is 21037609. The next prime is 21037631. The reversal of 21037613 is 31673012.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 18003049 + 3034564 = 4243^2 + 1742^2 .

It is a cyclic number.

It is not a de Polignac number, because 21037613 - 2² = 21037609 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21037603) 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, 43406 + ... + 43887.

It is an arithmetic number, because the mean of its divisors is an integer number (5281287).

Almost surely, 2^21037613 is an apocalyptic number.

It is an amenable number.

21037613 is a deficient number, since it is larger than the sum of its proper divisors (87535).

21037613 is an equidigital number, since it uses as much as digits as its factorization.

21037613 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 87534.

The product of its (nonzero) digits is 756, while the sum is 23.

The square root of 21037613 is about 4586.6777737269. The cubic root of 21037613 is about 276.0570359267.

The spelling of 21037613 in words is "twenty-one million, thirty-seven thousand, six hundred thirteen".