81278220 has 24 divisors (see below), whose sum is σ = 227579184. Its totient is φ = 21674176.

The previous prime is 81278209. The next prime is 81278243. The reversal of 81278220 is 2287218.

It is a happy number.

It is a super-2 number, since 2×81278220² = 13212298092736800, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (30).

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 in 7 ways as a sum of consecutive naturals, for example, 677259 + ... + 677378.

It is an arithmetic number, because the mean of its divisors is an integer number (9482466).

Almost surely, 2^81278220 is an apocalyptic number.

It is an amenable number.

81278220 is an abundant number, since it is smaller than the sum of its proper divisors (146300964).

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

81278220 is a wasteful number, since it uses less digits than its factorization.

81278220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1354649 (or 1354647 counting only the distinct ones).

The product of its (nonzero) digits is 3584, while the sum is 30.

The square root of 81278220 is about 9015.4434167156. The cubic root of 81278220 is about 433.1696910047.

The spelling of 81278220 in words is "eighty-one million, two hundred seventy-eight thousand, two hundred twenty".