66515840 has 64 divisors (see below), whose sum is σ = 162779760. Its totient is φ = 25976832.

The previous prime is 66515837. The next prime is 66515843. The reversal of 66515840 is 4851566.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (66515837) and next prime (66515843).

It is a tau number, because it is divible by the number of its divisors (64).

It is a self number, because there is not a number n which added to its sum of digits gives 66515840.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66515843) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 26312 + ... + 28728.

Almost surely, 2^66515840 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 66515840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (81389880).

66515840 is an abundant number, since it is smaller than the sum of its proper divisors (96263920).

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

66515840 is a wasteful number, since it uses less digits than its factorization.

66515840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2479 (or 2467 counting only the distinct ones).

The product of its (nonzero) digits is 28800, while the sum is 35.

The square root of 66515840 is about 8155.7243700361. The cubic root of 66515840 is about 405.1741160601.

The spelling of 66515840 in words is "sixty-six million, five hundred fifteen thousand, eight hundred forty".