81139555 has 64 divisors (see below), whose sum is σ = 125411328. Its totient is φ = 49121280.

The previous prime is 81139549. The next prime is 81139559. The reversal of 81139555 is 55593118.

It is not a de Polignac number, because 81139555 - 2⁵ = 81139523 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81139559) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 977544 + ... + 977626.

It is an arithmetic number, because the mean of its divisors is an integer number (1959552).

Almost surely, 2^81139555 is an apocalyptic number.

81139555 is a gapful number since it is divisible by the number (85) formed by its first and last digit.

81139555 is a deficient number, since it is larger than the sum of its proper divisors (44271773).

81139555 is a wasteful number, since it uses less digits than its factorization.

81139555 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 196.

The product of its digits is 27000, while the sum is 37.

The square root of 81139555 is about 9007.7497189920. The cubic root of 81139555 is about 432.9232138799.

The spelling of 81139555 in words is "eighty-one million, one hundred thirty-nine thousand, five hundred fifty-five".