721667640 has 32 divisors (see below), whose sum is σ = 2165003280. Its totient is φ = 192444672.

The previous prime is 721667537. The next prime is 721667651. The reversal of 721667640 is 46766127.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3006829 + ... + 3007068.

Almost surely, 2^721667640 is an apocalyptic number.

It is an amenable number.

721667640 is an abundant number, since it is smaller than the sum of its proper divisors (1443335640).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

721667640 is a wasteful number, since it uses less digits than its factorization.

721667640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6013911 (or 6013907 counting only the distinct ones).

The product of its (nonzero) digits is 84672, while the sum is 39.

The square root of 721667640 is about 26863.8723939792. The cubic root of 721667640 is about 896.9723944381.

The spelling of 721667640 in words is "seven hundred twenty-one million, six hundred sixty-seven thousand, six hundred forty".