81491779 has 12 divisors (see below), whose sum is σ = 86814840. Its totient is φ = 76494456.

The previous prime is 81491771. The next prime is 81491801. The reversal of 81491779 is 97719418.

It is a powerful number, because all its prime factors have an exponent greater than 1 and also an Achilles number because it is not a perfect power.

It is not a de Polignac number, because 81491779 - 2³ = 81491771 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81491771) 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, 747577 + ... + 747685.

It is an arithmetic number, because the mean of its divisors is an integer number (7234570).

Almost surely, 2^81491779 is an apocalyptic number.

81491779 is a deficient number, since it is larger than the sum of its proper divisors (5323061).

81491779 is an frugal number, since it uses more digits than its factorization.

81491779 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 275 (or 128 counting only the distinct ones).

The product of its digits is 127008, while the sum is 46.

The square root of 81491779 is about 9027.2797120727. The cubic root of 81491779 is about 433.5487445116.

The spelling of 81491779 in words is "eighty-one million, four hundred ninety-one thousand, seven hundred seventy-nine".