81155779 has 4 divisors (see below), whose sum is σ = 82267576. Its totient is φ = 80043984.

The previous prime is 81155777. The next prime is 81155791. The reversal of 81155779 is 97755118.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 97755118 = 2 ⋅48877559.

It is a cyclic number.

It is not a de Polignac number, because 81155779 - 2¹ = 81155777 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81155777) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 555789 + ... + 555934.

It is an arithmetic number, because the mean of its divisors is an integer number (20566894).

Almost surely, 2^81155779 is an apocalyptic number.

81155779 is a deficient number, since it is larger than the sum of its proper divisors (1111797).

81155779 is a wasteful number, since it uses less digits than its factorization.

81155779 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1111796.

The product of its digits is 88200, while the sum is 43.

The square root of 81155779 is about 9008.6502318605. The cubic root of 81155779 is about 432.9520665488.

The spelling of 81155779 in words is "eighty-one million, one hundred fifty-five thousand, seven hundred seventy-nine".