66561264 has 400 divisors, whose sum is σ = 259269120. Its totient is φ = 15966720.

The previous prime is 66561251. The next prime is 66561277. The reversal of 66561264 is 46216566.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (66561251) and next prime (66561277).

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

Its product of digits (51840) is a multiple of the sum of its prime factors (90).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 2295202 + ... + 2295230.

Almost surely, 2^66561264 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 66561264, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (129634560).

66561264 is an abundant number, since it is smaller than the sum of its proper divisors (192707856).

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

66561264 is a wasteful number, since it uses less digits than its factorization.

66561264 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 90 (or 75 counting only the distinct ones).

The product of its digits is 51840, while the sum is 36.

The square root of 66561264 is about 8158.5086872541. The cubic root of 66561264 is about 405.2663268834.

The spelling of 66561264 in words is "sixty-six million, five hundred sixty-one thousand, two hundred sixty-four".