1611981 has 20 divisors (see below), whose sum is σ = 2752992. Its totient is φ = 920808.

The previous prime is 1611971. The next prime is 1612007. The reversal of 1611981 is 1891161.

It is not a de Polignac number, because 1611981 - 2⁵ = 1611949 is a prime.

It is a super-2 number, since 2×1611981² = 5196965488722, which contains 22 as substring.

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Curzon number.

1611981 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1611901) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 855 + ... + 1988.

2^1611981 is an apocalyptic number.

It is an amenable number.

1611981 is a deficient number, since it is larger than the sum of its proper divisors (1141011).

1611981 is an equidigital number, since it uses as much as digits as its factorization.

1611981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2862 (or 2853 counting only the distinct ones).

The product of its digits is 432, while the sum is 27.

The square root of 1611981 is about 1269.6381374234. The cubic root of 1611981 is about 117.2519226578.

The spelling of 1611981 in words is "one million, six hundred eleven thousand, nine hundred eighty-one".