81521420250 has 32 divisors (see below), whose sum is σ = 203477466816. Its totient is φ = 21739045200.

The previous prime is 81521420249. The next prime is 81521420293. The reversal of 81521420250 is 5202412518.

It is a super-2 number, since 2×81521420250² (a number of 23 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 54346864 + ... + 54348363.

It is an arithmetic number, because the mean of its divisors is an integer number (6358670838).

Almost surely, 2^81521420250 is an apocalyptic number.

81521420250 is an abundant number, since it is smaller than the sum of its proper divisors (121956046566).

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

81521420250 is a wasteful number, since it uses less digits than its factorization.

81521420250 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 108695247 (or 108695237 counting only the distinct ones).

The product of its (nonzero) digits is 6400, while the sum is 30.

Adding to 81521420250 its reverse (5202412518), we get a palindrome (86723832768).

The spelling of 81521420250 in words is "eighty-one billion, five hundred twenty-one million, four hundred twenty thousand, two hundred fifty".