81211790 has 32 divisors (see below), whose sum is σ = 160272000. Its totient is φ = 29383200.

The previous prime is 81211787. The next prime is 81211799. The reversal of 81211790 is 9711218.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81211799) 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, 21461 + ... + 24959.

It is an arithmetic number, because the mean of its divisors is an integer number (5008500).

Almost surely, 2^81211790 is an apocalyptic number.

81211790 is a deficient number, since it is larger than the sum of its proper divisors (79060210).

81211790 is a wasteful number, since it uses less digits than its factorization.

81211790 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3728.

The product of its (nonzero) digits is 1008, while the sum is 29.

The square root of 81211790 is about 9011.7584299625. The cubic root of 81211790 is about 433.0516466476.

The spelling of 81211790 in words is "eighty-one million, two hundred eleven thousand, seven hundred ninety".