721625209 has 2 divisors, whose sum is σ = 721625210. Its totient is φ = 721625208.

The previous prime is 721625147. The next prime is 721625239. The reversal of 721625209 is 902526127.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 720117225 + 1507984 = 26835^2 + 1228^2 .

It is a cyclic number.

It is not a de Polignac number, because 721625209 - 2⁷ = 721625081 is a prime.

It is not a weakly prime, because it can be changed into another prime (721625239) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 360812604 + 360812605.

It is an arithmetic number, because the mean of its divisors is an integer number (360812605).

Almost surely, 2^721625209 is an apocalyptic number.

It is an amenable number.

721625209 is a deficient number, since it is larger than the sum of its proper divisors (1).

721625209 is an equidigital number, since it uses as much as digits as its factorization.

721625209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 15120, while the sum is 34.

The square root of 721625209 is about 26863.0826414245. The cubic root of 721625209 is about 896.9548147012.

The spelling of 721625209 in words is "seven hundred twenty-one million, six hundred twenty-five thousand, two hundred nine".