81521250 has 40 divisors (see below), whose sum is σ = 203747280. Its totient is φ = 21738000.

The previous prime is 81521213. The next prime is 81521281. The reversal of 81521250 is 5212518.

It is a self number, because there is not a number n which added to its sum of digits gives 81521250.

It is an unprimeable number.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 7120 + ... + 14619.

It is an arithmetic number, because the mean of its divisors is an integer number (5093682).

Almost surely, 2^81521250 is an apocalyptic number.

81521250 is an abundant number, since it is smaller than the sum of its proper divisors (122226030).

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

81521250 is a wasteful number, since it uses less digits than its factorization.

81521250 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21764 (or 21749 counting only the distinct ones).

The product of its (nonzero) digits is 800, while the sum is 24.

The square root of 81521250 is about 9028.9118945751. The cubic root of 81521250 is about 433.6010016237.

Adding to 81521250 its reverse (5212518), we get a palindrome (86733768).

The spelling of 81521250 in words is "eighty-one million, five hundred twenty-one thousand, two hundred fifty".