20721713 has 2 divisors, whose sum is σ = 20721714. Its totient is φ = 20721712.

The previous prime is 20721683. The next prime is 20721719. The reversal of 20721713 is 31712702.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18215824 + 2505889 = 4268^2 + 1583^2 .

It is a cyclic number.

It is not a de Polignac number, because 20721713 - 2²⁴ = 3944497 is a prime.

It is not a weakly prime, because it can be changed into another prime (20721719) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10360856 + 10360857.

It is an arithmetic number, because the mean of its divisors is an integer number (10360857).

Almost surely, 2^20721713 is an apocalyptic number.

It is an amenable number.

20721713 is a deficient number, since it is larger than the sum of its proper divisors (1).

20721713 is an equidigital number, since it uses as much as digits as its factorization.

20721713 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 588, while the sum is 23.

The square root of 20721713 is about 4552.1108290550. The cubic root of 20721713 is about 274.6683075265.

The spelling of 20721713 in words is "twenty million, seven hundred twenty-one thousand, seven hundred thirteen".