81621500 has 24 divisors (see below), whose sum is σ = 178262448. Its totient is φ = 32648400.

The previous prime is 81621497. The next prime is 81621509. The reversal of 81621500 is 512618.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81621509) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 81122 + ... + 82121.

It is an arithmetic number, because the mean of its divisors is an integer number (7427602).

Almost surely, 2^81621500 is an apocalyptic number.

It is an amenable number.

81621500 is an abundant number, since it is smaller than the sum of its proper divisors (96640948).

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

81621500 is a wasteful number, since it uses less digits than its factorization.

81621500 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 163262 (or 163250 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 23.

The square root of 81621500 is about 9034.4617991334. The cubic root of 81621500 is about 433.7786677506.

The spelling of 81621500 in words is "eighty-one million, six hundred twenty-one thousand, five hundred".