81272820 has 24 divisors (see below), whose sum is σ = 227564064. Its totient is φ = 21672736.

The previous prime is 81272773. The next prime is 81272827. The reversal of 81272820 is 2827218.

It is a happy number.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81272827) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 677214 + ... + 677333.

It is an arithmetic number, because the mean of its divisors is an integer number (9481836).

Almost surely, 2^81272820 is an apocalyptic number.

It is an amenable number.

81272820 is an abundant number, since it is smaller than the sum of its proper divisors (146291244).

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

81272820 is a wasteful number, since it uses less digits than its factorization.

81272820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1354559 (or 1354557 counting only the distinct ones).

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

The square root of 81272820 is about 9015.1439256398. The cubic root of 81272820 is about 433.1600977495.

The spelling of 81272820 in words is "eighty-one million, two hundred seventy-two thousand, eight hundred twenty".