981721 has 12 divisors (see below), whose sum is σ = 1098732. Its totient is φ = 876096.

The previous prime is 981713. The next prime is 981731. The reversal of 981721 is 127189.

It is the 405-th star number.

It can be written as a sum of positive squares in 6 ways, for example, as 69696 + 912025 = 264^2 + 955^2 .

It is not a de Polignac number, because 981721 - 2³ = 981713 is a prime.

It is a super-2 number, since 2×981721² = 1927552243682, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 981721.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (981731) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 6175 + ... + 6331.

It is an arithmetic number, because the mean of its divisors is an integer number (91561).

2⁹⁸¹⁷²¹ is an apocalyptic number.

It is an amenable number.

981721 is a deficient number, since it is larger than the sum of its proper divisors (117011).

981721 is a wasteful number, since it uses less digits than its factorization.

981721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 220 (or 207 counting only the distinct ones).

The product of its digits is 1008, while the sum is 28.

The square root of 981721 is about 990.8183486391. The cubic root of 981721 is about 99.3869493694.

The spelling of 981721 in words is "nine hundred eighty-one thousand, seven hundred twenty-one".