81207820 has 12 divisors (see below), whose sum is σ = 170536464. Its totient is φ = 32483120.

The previous prime is 81207809. The next prime is 81207821. The reversal of 81207820 is 2870218.

It is not an unprimeable number, because it can be changed into a prime (81207821) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 2030176 + ... + 2030215.

It is an arithmetic number, because the mean of its divisors is an integer number (14211372).

Almost surely, 2^81207820 is an apocalyptic number.

It is an amenable number.

81207820 is an abundant number, since it is smaller than the sum of its proper divisors (89328644).

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

81207820 is a wasteful number, since it uses less digits than its factorization.

81207820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4060400 (or 4060398 counting only the distinct ones).

The product of its (nonzero) digits is 1792, while the sum is 28.

The square root of 81207820 is about 9011.5381594931. The cubic root of 81207820 is about 433.0445900242.

The spelling of 81207820 in words is "eighty-one million, two hundred seven thousand, eight hundred twenty".