721031609 has 4 divisors (see below), whose sum is σ = 721118580. Its totient is φ = 720944640.

The previous prime is 721031603. The next prime is 721031629. The reversal of 721031609 is 906130127.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 906130127 = 7 ⋅129447161.

It can be written as a sum of positive squares in 2 ways, for example, as 580087225 + 140944384 = 24085^2 + 11872^2 .

It is a cyclic number.

It is not a de Polignac number, because 721031609 - 2⁴ = 721031593 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (721031603) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 29564 + ... + 48125.

It is an arithmetic number, because the mean of its divisors is an integer number (180279645).

Almost surely, 2^721031609 is an apocalyptic number.

It is an amenable number.

721031609 is a deficient number, since it is larger than the sum of its proper divisors (86971).

721031609 is an equidigital number, since it uses as much as digits as its factorization.

721031609 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 86970.

The product of its (nonzero) digits is 2268, while the sum is 29.

The square root of 721031609 is about 26852.0317480819. The cubic root of 721031609 is about 896.7088059103.

The spelling of 721031609 in words is "seven hundred twenty-one million, thirty-one thousand, six hundred nine".