721428 has 24 divisors (see below), whose sum is σ = 1706880. Its totient is φ = 237120.

The previous prime is 721397. The next prime is 721439. The reversal of 721428 is 824127.

It is an Ulam number.

It is a junction number, because it is equal to n+sod(n) for n = 721398 and 721407.

It is a congruent number.

It is an unprimeable number.

721428 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 568 + ... + 1328.

It is an arithmetic number, because the mean of its divisors is an integer number (71120).

2⁷²¹⁴²⁸ is an apocalyptic number.

It is an amenable number.

721428 is an abundant number, since it is smaller than the sum of its proper divisors (985452).

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

721428 is a wasteful number, since it uses less digits than its factorization.

721428 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 847 (or 845 counting only the distinct ones).

The product of its digits is 896, while the sum is 24.

The square root of 721428 is about 849.3691776842. The cubic root of 721428 is about 89.6873099301.

The spelling of 721428 in words is "seven hundred twenty-one thousand, four hundred twenty-eight".