721665774 has 48 divisors (see below), whose sum is σ = 1628735472. Its totient is φ = 239485248.

The previous prime is 721665767. The next prime is 721665781. The reversal of 721665774 is 477566127.

721665774 is a `hidden beast` number, since 72 + 1 + 6 + 6 + 577 + 4 = 666.

It is an interprime number because it is at equal distance from previous prime (721665767) and next prime (721665781).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 110052 + ... + 116424.

It is an arithmetic number, because the mean of its divisors is an integer number (33931989).

Almost surely, 2^721665774 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 721665774, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (814367736).

721665774 is an abundant number, since it is smaller than the sum of its proper divisors (907069698).

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

721665774 is a wasteful number, since it uses less digits than its factorization.

721665774 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6623 (or 6611 counting only the distinct ones).

The product of its digits is 493920, while the sum is 45.

The square root of 721665774 is about 26863.8376632975. The cubic root of 721665774 is about 896.9716213435.

The spelling of 721665774 in words is "seven hundred twenty-one million, six hundred sixty-five thousand, seven hundred seventy-four".