20721313 has 8 divisors (see below), whose sum is σ = 21656448. Its totient is φ = 19806864.

The previous prime is 20721301. The next prime is 20721319. The reversal of 20721313 is 31312702.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20721313 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20721319) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3106 + ... + 7147.

It is an arithmetic number, because the mean of its divisors is an integer number (2707056).

Almost surely, 2^20721313 is an apocalyptic number.

It is an amenable number.

20721313 is a deficient number, since it is larger than the sum of its proper divisors (935135).

20721313 is a wasteful number, since it uses less digits than its factorization.

20721313 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10343.

The product of its (nonzero) digits is 252, while the sum is 19.

The square root of 20721313 is about 4552.0668931816. The cubic root of 20721313 is about 274.6665401689. Note that the first 3 decimals are identical.

The spelling of 20721313 in words is "twenty million, seven hundred twenty-one thousand, three hundred thirteen".