721725721 has 8 divisors (see below), whose sum is σ = 733428864. Its totient is φ = 710065440.

The previous prime is 721725713. The next prime is 721725731. The reversal of 721725721 is 127527127.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 721725721 - 2³ = 721725713 is a prime.

It is not an unprimeable number, because it can be changed into a prime (721725731) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 24141 + ... + 45013.

It is an arithmetic number, because the mean of its divisors is an integer number (91678608).

Almost surely, 2^721725721 is an apocalyptic number.

721725721 is a gapful number since it is divisible by the number (71) formed by its first and last digit.

It is an amenable number.

721725721 is a deficient number, since it is larger than the sum of its proper divisors (11703143).

721725721 is a wasteful number, since it uses less digits than its factorization.

721725721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21431.

The product of its digits is 13720, while the sum is 34.

The square root of 721725721 is about 26864.9533965723. The cubic root of 721725721 is about 896.9964570643.

The spelling of 721725721 in words is "seven hundred twenty-one million, seven hundred twenty-five thousand, seven hundred twenty-one".