721826640 has 140 divisors (see below), whose sum is σ = 2516422644. Its totient is φ = 192471552.

The previous prime is 721826639. The next prime is 721826669. The reversal of 721826640 is 46628127.

721826640 is a `hidden beast` number, since 7 + 2 + 1 + 8 + 2 + 6 + 640 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 162409536 + 559417104 = 12744^2 + 23652^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 721826595 and 721826604.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 27 ways as a sum of consecutive naturals, for example, 52132 + ... + 64508.

Almost surely, 2^721826640 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 721826640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1258211322).

721826640 is an abundant number, since it is smaller than the sum of its proper divisors (1794596004).

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

721826640 is a wasteful number, since it uses less digits than its factorization.

721826640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12408 (or 12387 counting only the distinct ones).

The product of its (nonzero) digits is 32256, while the sum is 36.

The square root of 721826640 is about 26866.8315958544. The cubic root of 721826640 is about 897.0382641589.

The spelling of 721826640 in words is "seven hundred twenty-one million, eight hundred twenty-six thousand, six hundred forty".