1809981 has 12 divisors (see below), whose sum is σ = 2647008. Its totient is φ = 1191624.

The previous prime is 1809979. The next prime is 1809991. The reversal of 1809981 is 1899081.

It is not a de Polignac number, because 1809981 - 2¹ = 1809979 is a prime.

It is a super-2 number, since 2×1809981² = 6552062440722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1809901) 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, 465 + ... + 1958.

It is an arithmetic number, because the mean of its divisors is an integer number (220584).

2^1809981 is an apocalyptic number.

It is an amenable number.

1809981 is a deficient number, since it is larger than the sum of its proper divisors (837027).

1809981 is a wasteful number, since it uses less digits than its factorization.

1809981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2512 (or 2509 counting only the distinct ones).

The product of its (nonzero) digits is 5184, while the sum is 36.

The square root of 1809981 is about 1345.3553433945. The cubic root of 1809981 is about 121.8684643438.

The spelling of 1809981 in words is "one million, eight hundred nine thousand, nine hundred eighty-one".