81801562 has 4 divisors (see below), whose sum is σ = 122702346. Its totient is φ = 40900780.

The previous prime is 81801541. The next prime is 81801581. The reversal of 81801562 is 26510818.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 26510818 = 2 ⋅13255409.

It can be written as a sum of positive squares in only one way, i.e., 79548561 + 2253001 = 8919^2 + 1501^2 .

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

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 as a sum of consecutive naturals, namely, 20450389 + ... + 20450392.

Almost surely, 2^81801562 is an apocalyptic number.

81801562 is a deficient number, since it is larger than the sum of its proper divisors (40900784).

81801562 is a wasteful number, since it uses less digits than its factorization.

81801562 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40900783.

The product of its (nonzero) digits is 3840, while the sum is 31.

The square root of 81801562 is about 9044.4215956577. The cubic root of 81801562 is about 434.0974141939.

The spelling of 81801562 in words is "eighty-one million, eight hundred one thousand, five hundred sixty-two".