81491139 has 12 divisors (see below), whose sum is σ = 122827536. Its totient is φ = 51965232.

The previous prime is 81491119. The next prime is 81491147. The reversal of 81491139 is 93119418.

It is not a de Polignac number, because 81491139 - 2⁸ = 81490883 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81491119) 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, 196632 + ... + 197045.

It is an arithmetic number, because the mean of its divisors is an integer number (10235628).

Almost surely, 2^81491139 is an apocalyptic number.

81491139 is a deficient number, since it is larger than the sum of its proper divisors (41336397).

81491139 is a wasteful number, since it uses less digits than its factorization.

81491139 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 393706 (or 393703 counting only the distinct ones).

The product of its digits is 7776, while the sum is 36.

The square root of 81491139 is about 9027.2442638936. The cubic root of 81491139 is about 433.5476095426.

The spelling of 81491139 in words is "eighty-one million, four hundred ninety-one thousand, one hundred thirty-nine".