721901 has 4 divisors (see below), whose sum is σ = 753312. Its totient is φ = 690492.

The previous prime is 721891. The next prime is 721909. The reversal of 721901 is 109127.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 721901 - 2¹⁰ = 720877 is a prime.

It is a super-2 number, since 2×721901² = 1042282107602, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 721901.

It is not an unprimeable number, because it can be changed into a prime (721909) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 15671 + ... + 15716.

It is an arithmetic number, because the mean of its divisors is an integer number (188328).

2⁷²¹⁹⁰¹ is an apocalyptic number.

It is an amenable number.

721901 is a deficient number, since it is larger than the sum of its proper divisors (31411).

721901 is a wasteful number, since it uses less digits than its factorization.

721901 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31410.

The product of its (nonzero) digits is 126, while the sum is 20.

The square root of 721901 is about 849.6475739976. The cubic root of 721901 is about 89.7069066326.

The spelling of 721901 in words is "seven hundred twenty-one thousand, nine hundred one".