81621100 has 36 divisors (see below), whose sum is σ = 193222008. Its totient is φ = 29680000.

The previous prime is 81621091. The next prime is 81621107. The reversal of 81621100 is 112618.

It is not an unprimeable number, because it can be changed into a prime (81621107) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 36001 + ... + 38200.

It is an arithmetic number, because the mean of its divisors is an integer number (5367278).

Almost surely, 2^81621100 is an apocalyptic number.

It is an amenable number.

81621100 is an abundant number, since it is smaller than the sum of its proper divisors (111600908).

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

81621100 is a wasteful number, since it uses less digits than its factorization.

81621100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 74226 (or 74219 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 19.

The square root of 81621100 is about 9034.4396616503. The cubic root of 81621100 is about 433.7779591475. Note that the first 3 decimals are identical.

Adding to 81621100 its reverse (112618), we get a palindrome (81733718).

The spelling of 81621100 in words is "eighty-one million, six hundred twenty-one thousand, one hundred".