721613640 has 64 divisors (see below), whose sum is σ = 2361648960. Its totient is φ = 174936320.

The previous prime is 721613639. The next prime is 721613663. The reversal of 721613640 is 46316127.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 721613598 and 721613607.

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 15 ways as a sum of consecutive naturals, for example, 272019 + ... + 274658.

It is an arithmetic number, because the mean of its divisors is an integer number (36900765).

Almost surely, 2^721613640 is an apocalyptic number.

It is an amenable number.

721613640 is an abundant number, since it is smaller than the sum of its proper divisors (1640035320).

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

721613640 is a wasteful number, since it uses less digits than its factorization.

721613640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 546702 (or 546698 counting only the distinct ones).

The product of its (nonzero) digits is 6048, while the sum is 30.

The square root of 721613640 is about 26862.8673078657. The cubic root of 721613640 is about 896.9500213886.

Adding to 721613640 its reverse (46316127), we get a palindrome (767929767).

The spelling of 721613640 in words is "seven hundred twenty-one million, six hundred thirteen thousand, six hundred forty".