81637738 has 32 divisors (see below), whose sum is σ = 151167744. Its totient is φ = 32199552.

The previous prime is 81637729. The next prime is 81637739. The reversal of 81637738 is 83773618.

It is a Smith number, since the sum of its digits (43) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a junction number, because it is equal to n+sod(n) for n = 81637694 and 81637703.

It is not an unprimeable number, because it can be changed into a prime (81637739) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 111931 + ... + 112657.

It is an arithmetic number, because the mean of its divisors is an integer number (4723992).

Almost surely, 2^81637738 is an apocalyptic number.

81637738 is a deficient number, since it is larger than the sum of its proper divisors (69530006).

81637738 is a wasteful number, since it uses less digits than its factorization.

81637738 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1366.

The product of its digits is 169344, while the sum is 43.

The square root of 81637738 is about 9035.3604244656. The cubic root of 81637738 is about 433.8074315402.

The spelling of 81637738 in words is "eighty-one million, six hundred thirty-seven thousand, seven hundred thirty-eight".