81561758 has 8 divisors (see below), whose sum is σ = 124348440. Its totient is φ = 40112280.

The previous prime is 81561731. The next prime is 81561761. The reversal of 81561758 is 85716518.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 334148 + ... + 334391.

It is an arithmetic number, because the mean of its divisors is an integer number (15543555).

Almost surely, 2^81561758 is an apocalyptic number.

81561758 is a deficient number, since it is larger than the sum of its proper divisors (42786682).

81561758 is a wasteful number, since it uses less digits than its factorization.

81561758 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 668602.

The product of its digits is 67200, while the sum is 41.

The square root of 81561758 is about 9031.1548541701. The cubic root of 81561758 is about 433.6728086717.

The spelling of 81561758 in words is "eighty-one million, five hundred sixty-one thousand, seven hundred fifty-eight".