81723751 has 4 divisors (see below), whose sum is σ = 81777472. Its totient is φ = 81670032.

The previous prime is 81723749. The next prime is 81723757. The reversal of 81723751 is 15732718.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81723751 - 2¹ = 81723749 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81723757) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 24510 + ... + 27643.

It is an arithmetic number, because the mean of its divisors is an integer number (20444368).

Almost surely, 2^81723751 is an apocalyptic number.

81723751 is a deficient number, since it is larger than the sum of its proper divisors (53721).

81723751 is a wasteful number, since it uses less digits than its factorization.

81723751 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 53720.

The product of its digits is 11760, while the sum is 34.

The square root of 81723751 is about 9040.1189704561. The cubic root of 81723751 is about 433.9597303133.

The spelling of 81723751 in words is "eighty-one million, seven hundred twenty-three thousand, seven hundred fifty-one".