81563786 has 4 divisors (see below), whose sum is σ = 122345682. Its totient is φ = 40781892.

The previous prime is 81563761. The next prime is 81563809. The reversal of 81563786 is 68736518.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 68736518 = 2 ⋅34368259.

It can be written as a sum of positive squares in only one way, i.e., 43309561 + 38254225 = 6581^2 + 6185^2 .

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, 20390945 + ... + 20390948.

Almost surely, 2^81563786 is an apocalyptic number.

81563786 is a deficient number, since it is larger than the sum of its proper divisors (40781896).

81563786 is a wasteful number, since it uses less digits than its factorization.

81563786 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40781895.

The product of its digits is 241920, while the sum is 44.

The square root of 81563786 is about 9031.2671314716. The cubic root of 81563786 is about 433.6764030080.

The spelling of 81563786 in words is "eighty-one million, five hundred sixty-three thousand, seven hundred eighty-six".