665540550 has 252 divisors, whose sum is σ = 2018749140. Its totient is φ = 162712800.

The previous prime is 665540537. The next prime is 665540587. The reversal of 665540550 is 55045566.

It is a happy number.

665540550 is a `hidden beast` number, since 6 + 65 + 5 + 40 + 550 = 666.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 125 ways as a sum of consecutive naturals, for example, 21469035 + ... + 21469065.

Almost surely, 2^665540550 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 665540550, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1009374570).

665540550 is an abundant number, since it is smaller than the sum of its proper divisors (1353208590).

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

665540550 is a wasteful number, since it uses less digits than its factorization.

665540550 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 111 (or 60 counting only the distinct ones).

The product of its (nonzero) digits is 90000, while the sum is 36.

The square root of 665540550 is about 25798.0726024252. The cubic root of 665540550 is about 873.0883107603.

The spelling of 665540550 in words is "six hundred sixty-five million, five hundred forty thousand, five hundred fifty".