81780386 has 4 divisors (see below), whose sum is σ = 122670582. Its totient is φ = 40890192.

The previous prime is 81780379. The next prime is 81780403. The reversal of 81780386 is 68308718.

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

It can be written as a sum of positive squares in only one way, i.e., 61701025 + 20079361 = 7855^2 + 4481^2 .

It is a Curzon number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20445095 + ... + 20445098.

Almost surely, 2^81780386 is an apocalyptic number.

81780386 is a deficient number, since it is larger than the sum of its proper divisors (40890196).

81780386 is a wasteful number, since it uses less digits than its factorization.

81780386 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40890195.

The product of its (nonzero) digits is 64512, while the sum is 41.

The square root of 81780386 is about 9043.2508535371. The cubic root of 81780386 is about 434.0599526428.

The spelling of 81780386 in words is "eighty-one million, seven hundred eighty thousand, three hundred eighty-six".