921981 has 8 divisors (see below), whose sum is σ = 1235520. Its totient is φ = 611552.

The previous prime is 921959. The next prime is 921989. The reversal of 921981 is 189129.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 921981 - 2¹⁰ = 920957 is a prime.

It is a super-2 number, since 2×921981² = 1700097928722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (921989) by changing a digit.

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

It is an upside-down number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 40 + ... + 1358.

It is an arithmetic number, because the mean of its divisors is an integer number (154440).

2⁹²¹⁹⁸¹ is an apocalyptic number.

It is an amenable number.

921981 is a deficient number, since it is larger than the sum of its proper divisors (313539).

921981 is a wasteful number, since it uses less digits than its factorization.

921981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1555.

The product of its digits is 1296, while the sum is 30.

The square root of 921981 is about 960.1984169952. The cubic root of 921981 is about 97.3286404922.

The spelling of 921981 in words is "nine hundred twenty-one thousand, nine hundred eighty-one".