81139188 has 24 divisors (see below), whose sum is σ = 203888608. Its totient is φ = 24965856.

The previous prime is 81139171. The next prime is 81139199. The reversal of 81139188 is 88193118.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 259906 + ... + 260217.

Almost surely, 2^81139188 is an apocalyptic number.

It is an amenable number.

81139188 is an abundant number, since it is smaller than the sum of its proper divisors (122749420).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81139188 is a wasteful number, since it uses less digits than its factorization.

81139188 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 520143 (or 520141 counting only the distinct ones).

The product of its digits is 13824, while the sum is 39.

The square root of 81139188 is about 9007.7293476214. The cubic root of 81139188 is about 432.9225611648.

The spelling of 81139188 in words is "eighty-one million, one hundred thirty-nine thousand, one hundred eighty-eight".