1661931 has 8 divisors (see below), whose sum is σ = 2462160. Its totient is φ = 1107936.

The previous prime is 1661917. The next prime is 1661939. The reversal of 1661931 is 1391661.

1661931 is a `hidden beast` number, since 16 + 619 + 31 = 666.

It is not a de Polignac number, because 1661931 - 2⁵ = 1661899 is a prime.

It is a super-3 number, since 3×1661931³ = 13770833301690052473, which contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 61553 = 1661931 / (1 + 6 + 6 + 1 + 9 + 3 + 1).

1661931 is a lucky number.

It is a junction number, because it is equal to n+sod(n) for n = 1661895 and 1661904.

It is not an unprimeable number, because it can be changed into a prime (1661939) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 30750 + ... + 30803.

It is an arithmetic number, because the mean of its divisors is an integer number (307770).

2^1661931 is an apocalyptic number.

1661931 is a deficient number, since it is larger than the sum of its proper divisors (800229).

1661931 is an equidigital number, since it uses as much as digits as its factorization.

1661931 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 61562 (or 61556 counting only the distinct ones).

The product of its digits is 972, while the sum is 27.

The square root of 1661931 is about 1289.1590282040. The cubic root of 1661931 is about 118.4507085493.

The spelling of 1661931 in words is "one million, six hundred sixty-one thousand, nine hundred thirty-one".