81388506 has 16 divisors (see below), whose sum is σ = 163399104. Its totient is φ = 27025824.

The previous prime is 81388499. The next prime is 81388511. The reversal of 81388506 is 60588318.

It is a happy 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, 24211 + ... + 27366.

It is an arithmetic number, because the mean of its divisors is an integer number (10212444).

Almost surely, 2^81388506 is an apocalyptic number.

81388506 is an abundant number, since it is smaller than the sum of its proper divisors (82010598).

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

81388506 is a wasteful number, since it uses less digits than its factorization.

81388506 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51845.

The product of its (nonzero) digits is 46080, while the sum is 39.

The square root of 81388506 is about 9021.5578477334. The cubic root of 81388506 is about 433.3655243673.

The spelling of 81388506 in words is "eighty-one million, three hundred eighty-eight thousand, five hundred six".