21028613 has 8 divisors (see below), whose sum is σ = 21603456. Its totient is φ = 20456800.

The previous prime is 21028597. The next prime is 21028619. The reversal of 21028613 is 31682012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21028613 - 2⁴ = 21028597 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 (21028619) 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 7 ways as a sum of consecutive naturals, for example, 22628 + ... + 23538.

It is an arithmetic number, because the mean of its divisors is an integer number (2700432).

Almost surely, 2^21028613 is an apocalyptic number.

It is an amenable number.

21028613 is a deficient number, since it is larger than the sum of its proper divisors (574843).

21028613 is an equidigital number, since it uses as much as digits as its factorization.

21028613 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1515.

The product of its (nonzero) digits is 576, while the sum is 23.

The square root of 21028613 is about 4585.6965664989. The cubic root of 21028613 is about 276.0176641009.

The spelling of 21028613 in words is "twenty-one million, twenty-eight thousand, six hundred thirteen".