81978511139 has 16 divisors (see below), whose sum is σ = 102908628480. Its totient is φ = 63674709120.

The previous prime is 81978511123. The next prime is 81978511157. The reversal of 81978511139 is 93111587918.

It is not a de Polignac number, because 81978511139 - 2⁴ = 81978511123 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81978511739) 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, 13396502 + ... + 13402619.

It is an arithmetic number, because the mean of its divisors is an integer number (6431789280).

Almost surely, 2^81978511139 is an apocalyptic number.

81978511139 is a deficient number, since it is larger than the sum of its proper divisors (20930117341).

81978511139 is a wasteful number, since it uses less digits than its factorization.

81978511139 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26799170.

The product of its digits is 544320, while the sum is 53.

The spelling of 81978511139 in words is "eighty-one billion, nine hundred seventy-eight million, five hundred eleven thousand, one hundred thirty-nine".