81491998 has 32 divisors (see below), whose sum is σ = 143481600. Its totient is φ = 34697880.

The previous prime is 81491987. The next prime is 81492011. The reversal of 81491998 is 89919418.

It is a Harshad number since it is a multiple of its sum of digits (49).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 144465 + ... + 145027.

It is an arithmetic number, because the mean of its divisors is an integer number (4483800).

Almost surely, 2^81491998 is an apocalyptic number.

81491998 is a deficient number, since it is larger than the sum of its proper divisors (61989602).

81491998 is a wasteful number, since it uses less digits than its factorization.

81491998 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 797 (or 783 counting only the distinct ones).

The product of its digits is 186624, while the sum is 49.

The square root of 81491998 is about 9027.2918419646. The cubic root of 81491998 is about 433.5491328824.

The spelling of 81491998 in words is "eighty-one million, four hundred ninety-one thousand, nine hundred ninety-eight".