81284920 has 32 divisors (see below), whose sum is σ = 183150000. Its totient is φ = 32467968.

The previous prime is 81284911. The next prime is 81284927. The reversal of 81284920 is 2948218.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81284927) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 49147 + ... + 50773.

Almost surely, 2^81284920 is an apocalyptic number.

It is an amenable number.

81284920 is an abundant number, since it is smaller than the sum of its proper divisors (101865080).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81284920 is a wasteful number, since it uses less digits than its factorization.

81284920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2887 (or 2883 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 34.

The square root of 81284920 is about 9015.8149936653. The cubic root of 81284920 is about 433.1815931567.

The spelling of 81284920 in words is "eighty-one million, two hundred eighty-four thousand, nine hundred twenty".