81821966 has 4 divisors (see below), whose sum is σ = 122732952. Its totient is φ = 40910982.

The previous prime is 81821953. The next prime is 81822007. The reversal of 81821966 is 66912818.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20455490 + ... + 20455493.

It is an arithmetic number, because the mean of its divisors is an integer number (30683238).

Almost surely, 2^81821966 is an apocalyptic number.

81821966 is a deficient number, since it is larger than the sum of its proper divisors (40910986).

81821966 is a wasteful number, since it uses less digits than its factorization.

81821966 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40910985.

The product of its digits is 41472, while the sum is 41.

The square root of 81821966 is about 9045.5495134348. The cubic root of 81821966 is about 434.1335039176.

The spelling of 81821966 in words is "eighty-one million, eight hundred twenty-one thousand, nine hundred sixty-six".