721801 has 4 divisors (see below), whose sum is σ = 723604. Its totient is φ = 720000.

The previous prime is 721793. The next prime is 721843. The reversal of 721801 is 108127.

721801 is a nontrivial binomial coefficient, being equal to C(1202, 2).

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 230400 + 491401 = 480^2 + 701^2 .

It is a 3-Lehmer number, since φ(721801) divides (721801-1)³.

It is a cyclic number.

It is not a de Polignac number, because 721801 - 2³ = 721793 is a prime.

It is a deceptive number, since it divides R₇₂₁₈₀₀.

It is not an unprimeable number, because it can be changed into a prime (721891) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1 + ... + 1201.

It is an arithmetic number, because the mean of its divisors is an integer number (180901).

It is a Poulet number, since it divides 2⁷²¹⁸⁰⁰-1.

2⁷²¹⁸⁰¹ is an apocalyptic number.

721801 is the 1201-st triangular number and also the 601-st hexagonal number.

721801 is the 401-st centered nonagonal number.

It is an amenable number.

721801 is a deficient number, since it is larger than the sum of its proper divisors (1803).

721801 is a wasteful number, since it uses less digits than its factorization.

721801 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1802.

The product of its (nonzero) digits is 112, while the sum is 19.

The square root of 721801 is about 849.5887240306. The cubic root of 721801 is about 89.7027642803.

Adding to 721801 its reverse (108127), we get a palindrome (829928).

The spelling of 721801 in words is "seven hundred twenty-one thousand, eight hundred one".