721810013 has 2 divisors, whose sum is σ = 721810014. Its totient is φ = 721810012.

The previous prime is 721810009. The next prime is 721810031. The reversal of 721810013 is 310018127.

721810013 = 18997² + 18998².

It is a happy number.

Together with next prime (721810031) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 360924004 + 360886009 = 18998^2 + 18997^2 .

It is a cyclic number.

It is not a de Polignac number, because 721810013 - 2² = 721810009 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (721810003) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 360905006 + 360905007.

It is an arithmetic number, because the mean of its divisors is an integer number (360905007).

Almost surely, 2^721810013 is an apocalyptic number.

721810013 is the 18998-th centered square number.

It is an amenable number.

721810013 is a deficient number, since it is larger than the sum of its proper divisors (1).

721810013 is an equidigital number, since it uses as much as digits as its factorization.

721810013 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 336, while the sum is 23.

The square root of 721810013 is about 26866.5221604881. The cubic root of 721810013 is about 897.0313764618.

The spelling of 721810013 in words is "seven hundred twenty-one million, eight hundred ten thousand, thirteen".