81205730 has 8 divisors (see below), whose sum is σ = 146170332. Its totient is φ = 32482288.

The previous prime is 81205727. The next prime is 81205739. The reversal of 81205730 is 3750218.

It can be written as a sum of positive squares in 2 ways, for example, as 80982001 + 223729 = 8999^2 + 473^2 .

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

It is a self number, because there is not a number n which added to its sum of digits gives 81205730.

It is not an unprimeable number, because it can be changed into a prime (81205739) 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, 4060277 + ... + 4060296.

Almost surely, 2^81205730 is an apocalyptic number.

81205730 is a deficient number, since it is larger than the sum of its proper divisors (64964602).

81205730 is a wasteful number, since it uses less digits than its factorization.

81205730 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8120580.

The product of its (nonzero) digits is 1680, while the sum is 26.

The square root of 81205730 is about 9011.4221963018. The cubic root of 81205730 is about 433.0408749840.

Adding to 81205730 its reverse (3750218), we get a palindrome (84955948).

The spelling of 81205730 in words is "eighty-one million, two hundred five thousand, seven hundred thirty".