66531840 has 80 divisors (see below), whose sum is σ = 212718528. Its totient is φ = 17739776.

The previous prime is 66531833. The next prime is 66531911. The reversal of 66531840 is 4813566.

It is a tau number, because it is divible by the number of its divisors (80).

It is a hoax number, since the sum of its digits (33) coincides with the sum of the digits of its distinct prime factors.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3349 + ... + 12011.

Almost surely, 2^66531840 is an apocalyptic number.

66531840 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 66531840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (106359264).

66531840 is an abundant number, since it is smaller than the sum of its proper divisors (146186688).

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

66531840 is an equidigital number, since it uses as much as digits as its factorization.

66531840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8689 (or 8673 counting only the distinct ones).

The product of its (nonzero) digits is 17280, while the sum is 33.

The square root of 66531840 is about 8156.7052171818. The cubic root of 66531840 is about 405.2066008844.

The spelling of 66531840 in words is "sixty-six million, five hundred thirty-one thousand, eight hundred forty".