21031613 has 4 divisors (see below), whose sum is σ = 22138560. Its totient is φ = 19924668.

The previous prime is 21031559. The next prime is 21031627. The reversal of 21031613 is 31613012.

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 21031613 - 2⁸ = 21031357 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21031591 and 21031600.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21031313) 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, 553445 + ... + 553482.

It is an arithmetic number, because the mean of its divisors is an integer number (5534640).

Almost surely, 2^21031613 is an apocalyptic number.

It is an amenable number.

21031613 is a deficient number, since it is larger than the sum of its proper divisors (1106947).

21031613 is a wasteful number, since it uses less digits than its factorization.

21031613 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1106946.

The product of its (nonzero) digits is 108, while the sum is 17.

The square root of 21031613 is about 4586.0236589010. The cubic root of 21031613 is about 276.0307892908.

Adding to 21031613 its reverse (31613012), we get a palindrome (52644625).

The spelling of 21031613 in words is "twenty-one million, thirty-one thousand, six hundred thirteen".