81142779 has 16 divisors (see below), whose sum is σ = 112501760. Its totient is φ = 51965280.

The previous prime is 81142777. The next prime is 81142799. The reversal of 81142779 is 97724118.

It is not a de Polignac number, because 81142779 - 2¹ = 81142777 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81142777) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 9789 + ... + 16065.

It is an arithmetic number, because the mean of its divisors is an integer number (7031360).

Almost surely, 2^81142779 is an apocalyptic number.

81142779 is a deficient number, since it is larger than the sum of its proper divisors (31358981).

81142779 is a wasteful number, since it uses less digits than its factorization.

81142779 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6450.

The product of its digits is 28224, while the sum is 39.

The square root of 81142779 is about 9007.9286742292. The cubic root of 81142779 is about 432.9289477293.

The spelling of 81142779 in words is "eighty-one million, one hundred forty-two thousand, seven hundred seventy-nine".