81533751 has 32 divisors (see below), whose sum is σ = 127991808. Its totient is φ = 45688320.

The previous prime is 81533747. The next prime is 81533791. The reversal of 81533751 is 15733518.

It is not a de Polignac number, because 81533751 - 2² = 81533747 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81533791) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 18570 + ... + 22536.

It is an arithmetic number, because the mean of its divisors is an integer number (3999744).

Almost surely, 2^81533751 is an apocalyptic number.

81533751 is a deficient number, since it is larger than the sum of its proper divisors (46458057).

81533751 is a wasteful number, since it uses less digits than its factorization.

81533751 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4031.

The product of its digits is 12600, while the sum is 33.

The square root of 81533751 is about 9029.6041441472. The cubic root of 81533751 is about 433.6231642258.

The spelling of 81533751 in words is "eighty-one million, five hundred thirty-three thousand, seven hundred fifty-one".