81212140 has 48 divisors (see below), whose sum is σ = 173859840. Its totient is φ = 31861440.

The previous prime is 81212119. The next prime is 81212141. The reversal of 81212140 is 4121218.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (81212141) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 364069 + ... + 364291.

It is an arithmetic number, because the mean of its divisors is an integer number (3622080).

Almost surely, 2^81212140 is an apocalyptic number.

It is an amenable number.

81212140 is an abundant number, since it is smaller than the sum of its proper divisors (92647700).

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

81212140 is a wasteful number, since it uses less digits than its factorization.

81212140 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 502 (or 500 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 19.

The square root of 81212140 is about 9011.7778490151. Note that the first 3 decimals coincide. The cubic root of 81212140 is about 433.0522687570.

Adding to 81212140 its reverse (4121218), we get a palindrome (85333358).

The spelling of 81212140 in words is "eighty-one million, two hundred twelve thousand, one hundred forty".