81787420225 has 27 divisors (see below), whose sum is σ = 117988620771. Its totient is φ = 56075938800.

The previous prime is 81787420217. The next prime is 81787420237. The reversal of 81787420225 is 52202478718.

It is a happy number.

The square root of 81787420225 is 285985.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 29443471281 + 52343948944 = 171591^2 + 228788^2 .

It is not a de Polignac number, because 81787420225 - 2³ = 81787420217 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 10005390 + ... + 10013560.

Almost surely, 2^81787420225 is an apocalyptic number.

81787420225 is the 285985-th square number.

81787420225 is the 142993-rd centered octagonal number.

It is an amenable number.

81787420225 is a deficient number, since it is larger than the sum of its proper divisors (36201200546).

81787420225 is an frugal number, since it uses more digits than its factorization.

81787420225 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16366 (or 8183 counting only the distinct ones).

The product of its (nonzero) digits is 501760, while the sum is 46.

The spelling of 81787420225 in words is "eighty-one billion, seven hundred eighty-seven million, four hundred twenty thousand, two hundred twenty-five".