891636390225 has 405 divisors, whose sum is σ = 2063168550417. Its totient is φ = 366948933120.

The previous prime is 891636390217. The next prime is 891636390287. The reversal of 891636390225 is 522093636198.

The square root of 891636390225 is 944265.

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

It can be written as a sum of positive squares in 4 ways, for example, as 20856269889 + 870780120336 = 144417^2 + 933156^2 .

It is not a de Polignac number, because 891636390225 - 2³ = 891636390217 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 404 ways as a sum of consecutive naturals, for example, 38766799564 + ... + 38766799586.

Almost surely, 2^891636390225 is an apocalyptic number.

891636390225 is a gapful number since it is divisible by the number (85) formed by its first and last digit.

891636390225 is the 944265-th square number.

891636390225 is the 472133-rd centered octagonal number.

It is an amenable number.

891636390225 is an abundant number, since it is smaller than the sum of its proper divisors (1171532160192).

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

891636390225 is an equidigital number, since it uses as much as digits as its factorization.

891636390225 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 156 (or 55 counting only the distinct ones).

The product of its (nonzero) digits is 4199040, while the sum is 54.

The spelling of 891636390225 in words is "eight hundred ninety-one billion, six hundred thirty-six million, three hundred ninety thousand, two hundred twenty-five".