666155520 has 240 divisors, whose sum is σ = 2389032360. Its totient is φ = 171343872.

The previous prime is 666155507. The next prime is 666155533. The reversal of 666155520 is 25551666.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (666155507) and next prime (666155533).

It can be written as a sum of positive squares in 4 ways, for example, as 625400064 + 40755456 = 25008^2 + 6384^2 .

It is a tau number, because it is divible by the number of its divisors (240).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 667662 + ... + 668658.

Almost surely, 2^666155520 is an apocalyptic number.

666155520 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 666155520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1194516180).

666155520 is an abundant number, since it is smaller than the sum of its proper divisors (1722876840).

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

666155520 is a wasteful number, since it uses less digits than its factorization.

666155520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1055 (or 1036 counting only the distinct ones).

The product of its (nonzero) digits is 54000, while the sum is 36.

The square root of 666155520 is about 25809.9887640425. The cubic root of 666155520 is about 873.3571437804.

The spelling of 666155520 in words is "six hundred sixty-six million, one hundred fifty-five thousand, five hundred twenty".