1981511 has 16 divisors (see below), whose sum is σ = 2376000. Its totient is φ = 1651104.

The previous prime is 1981493. The next prime is 1981513. The reversal of 1981511 is 1151891.

It is a de Polignac number, because none of the positive numbers 2^k-1981511 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1981513) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 18125 + ... + 18233.

It is an arithmetic number, because the mean of its divisors is an integer number (148500).

2^1981511 is an apocalyptic number.

1981511 is a deficient number, since it is larger than the sum of its proper divisors (394489).

1981511 is an equidigital number, since it uses as much as digits as its factorization.

1981511 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 183 (or 169 counting only the distinct ones).

The product of its digits is 360, while the sum is 26.

The square root of 1981511 is about 1407.6615360235. The cubic root of 1981511 is about 125.6026577595.

The spelling of 1981511 in words is "one million, nine hundred eighty-one thousand, five hundred eleven".