1981557 has 16 divisors (see below), whose sum is σ = 2976000. Its totient is φ = 1302912.

The previous prime is 1981547. The next prime is 1981583. The reversal of 1981557 is 7551891.

It is not a de Polignac number, because 1981557 - 2⁶ = 1981493 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1981517) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1669 + ... + 2597.

It is an arithmetic number, because the mean of its divisors is an integer number (186000).

2^1981557 is an apocalyptic number.

It is an amenable number.

1981557 is a deficient number, since it is larger than the sum of its proper divisors (994443).

1981557 is an equidigital number, since it uses as much as digits as its factorization.

1981557 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1017 (or 1011 counting only the distinct ones).

The product of its digits is 12600, while the sum is 36.

The square root of 1981557 is about 1407.6778750836. The cubic root of 1981557 is about 125.6036296908.

The spelling of 1981557 in words is "one million, nine hundred eighty-one thousand, five hundred fifty-seven".