81561726 has 24 divisors (see below), whose sum is σ = 184401360. Its totient is φ = 26005056.

The previous prime is 81561721. The next prime is 81561731. The reversal of 81561726 is 62716518.

81561726 is a `hidden beast` number, since 8 + 15 + 617 + 26 = 666.

It is an interprime number because it is at equal distance from previous prime (81561721) and next prime (81561731).

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81561721) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 98091 + ... + 98918.

It is an arithmetic number, because the mean of its divisors is an integer number (7683390).

Almost surely, 2^81561726 is an apocalyptic number.

81561726 is an abundant number, since it is smaller than the sum of its proper divisors (102839634).

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

81561726 is a wasteful number, since it uses less digits than its factorization.

81561726 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 197040 (or 197037 counting only the distinct ones).

The product of its digits is 20160, while the sum is 36.

The square root of 81561726 is about 9031.1530825250. The cubic root of 81561726 is about 433.6727519559.

The spelling of 81561726 in words is "eighty-one million, five hundred sixty-one thousand, seven hundred twenty-six".