66641664 has 72 divisors (see below), whose sum is σ = 186739840. Its totient is φ = 21040128.

The previous prime is 66641657. The next prime is 66641671. The reversal of 66641664 is 46614666.

It is an interprime number because it is at equal distance from previous prime (66641657) and next prime (66641671).

It is a super-2 number, since 2×66641664² = 8882222761377792, which contains 22 as substring.

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

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, 12309 + ... + 16875.

Almost surely, 2^66641664 is an apocalyptic number.

66641664 is a gapful number since it is divisible by the number (64) 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 66641664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (93369920).

66641664 is an abundant number, since it is smaller than the sum of its proper divisors (120098176).

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

66641664 is a wasteful number, since it uses less digits than its factorization.

66641664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4605 (or 4591 counting only the distinct ones).

The product of its digits is 124416, while the sum is 39.

The square root of 66641664 is about 8163.4345713064. The cubic root of 66641664 is about 405.4294362769.

The spelling of 66641664 in words is "sixty-six million, six hundred forty-one thousand, six hundred sixty-four".