81620109 has 16 divisors (see below), whose sum is σ = 122624640. Its totient is φ = 53645760.

The previous prime is 81620107. The next prime is 81620141. The reversal of 81620109 is 90102618.

It is not a de Polignac number, because 81620109 - 2¹ = 81620107 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81620101) 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, 19372 + ... + 23205.

It is an arithmetic number, because the mean of its divisors is an integer number (7664040).

Almost surely, 2^81620109 is an apocalyptic number.

It is an amenable number.

81620109 is a deficient number, since it is larger than the sum of its proper divisors (41004531).

81620109 is a wasteful number, since it uses less digits than its factorization.

81620109 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 42657 (or 42651 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 27.

The square root of 81620109 is about 9034.3848158023. The cubic root of 81620109 is about 433.7762035733.

The spelling of 81620109 in words is "eighty-one million, six hundred twenty thousand, one hundred nine".