81223885 has 8 divisors (see below), whose sum is σ = 97522200. Its totient is φ = 64943424.

The previous prime is 81223837. The next prime is 81223903. The reversal of 81223885 is 58832218.

81223885 is a nontrivial binomial coefficient, being equal to C(12746, 2).

It can be written as a sum of positive squares in 4 ways, for example, as 38019556 + 43204329 = 6166^2 + 6573^2 .

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81223885 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9559 + ... + 15931.

It is an arithmetic number, because the mean of its divisors is an integer number (12190275).

Almost surely, 2^81223885 is an apocalyptic number.

81223885 is the 12745-th triangular number and also the 6373-rd hexagonal number.

81223885 is the 4249-th centered nonagonal number.

It is an amenable number.

81223885 is a deficient number, since it is larger than the sum of its proper divisors (16298315).

81223885 is a wasteful number, since it uses less digits than its factorization.

81223885 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8927.

The product of its digits is 30720, while the sum is 37.

The square root of 81223885 is about 9012.4294726783. The cubic root of 81223885 is about 433.0731439354.

The spelling of 81223885 in words is "eighty-one million, two hundred twenty-three thousand, eight hundred eighty-five".