81723780 has 36 divisors (see below), whose sum is σ = 247896012. Its totient is φ = 21792960.

The previous prime is 81723773. The next prime is 81723797. The reversal of 81723780 is 8732718.

It can be written as a sum of positive squares in 2 ways, for example, as 37527876 + 44195904 = 6126^2 + 6648^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 226831 + ... + 227190.

Almost surely, 2^81723780 is an apocalyptic number.

It is an amenable number.

81723780 is an abundant number, since it is smaller than the sum of its proper divisors (166172232).

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

81723780 is a wasteful number, since it uses less digits than its factorization.

81723780 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 454036 (or 454031 counting only the distinct ones).

The product of its (nonzero) digits is 18816, while the sum is 36.

The square root of 81723780 is about 9040.1205744171. The cubic root of 81723780 is about 433.9597816441.

The spelling of 81723780 in words is "eighty-one million, seven hundred twenty-three thousand, seven hundred eighty".