81661734 has 144 divisors (see below), whose sum is σ = 236882880. Its totient is φ = 20049120.

The previous prime is 81661733. The next prime is 81661739. The reversal of 81661734 is 43716618.

81661734 is a `hidden beast` number, since 8 + 1 + 6 + 617 + 34 = 666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81661733) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 184117 + ... + 184559.

It is an arithmetic number, because the mean of its divisors is an integer number (1645020).

Almost surely, 2^81661734 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81661734, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (118441440).

81661734 is an abundant number, since it is smaller than the sum of its proper divisors (155221146).

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

81661734 is a wasteful number, since it uses less digits than its factorization.

81661734 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 495 (or 485 counting only the distinct ones).

The product of its digits is 24192, while the sum is 36.

The square root of 81661734 is about 9036.6882208030. The cubic root of 81661734 is about 433.8499307718.

Subtracting from 81661734 its reverse (43716618), we obtain a triangular number (37945116 = T₈₇₁₁).

The spelling of 81661734 in words is "eighty-one million, six hundred sixty-one thousand, seven hundred thirty-four".