721864 has 32 divisors (see below), whose sum is σ = 1592640. Its totient is φ = 302400.

The previous prime is 721859. The next prime is 721883. The reversal of 721864 is 468127.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 829 + ... + 1459.

It is an arithmetic number, because the mean of its divisors is an integer number (49770).

2⁷²¹⁸⁶⁴ 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 721864, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (796320).

721864 is an abundant number, since it is smaller than the sum of its proper divisors (870776).

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

721864 is a wasteful number, since it uses less digits than its factorization.

721864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 661 (or 657 counting only the distinct ones).

The product of its digits is 2688, while the sum is 28.

The square root of 721864 is about 849.6257999849. The cubic root of 721864 is about 89.7053740068.

It can be divided in two parts, 72 and 1864, that added together give a square (1936 = 44²).

The spelling of 721864 in words is "seven hundred twenty-one thousand, eight hundred sixty-four".