721081 has 4 divisors (see below), whose sum is σ = 732964. Its totient is φ = 709200.

The previous prime is 721079. The next prime is 721087. The reversal of 721081 is 180127.

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 55225 + 665856 = 235^2 + 816^2 .

It is a cyclic number.

It is not a de Polignac number, because 721081 - 2¹ = 721079 is a prime.

It is a super-2 number, since 2×721081² = 1039915617122, which contains 22 as substring.

It is a Duffinian number.

721081 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (721087) 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, 5850 + ... + 5971.

It is an arithmetic number, because the mean of its divisors is an integer number (183241).

2⁷²¹⁰⁸¹ is an apocalyptic number.

It is an amenable number.

721081 is a deficient number, since it is larger than the sum of its proper divisors (11883).

721081 is a wasteful number, since it uses less digits than its factorization.

721081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11882.

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

The square root of 721081 is about 849.1648838712. The cubic root of 721081 is about 89.6729280433.

The spelling of 721081 in words is "seven hundred twenty-one thousand, eighty-one".