66697664 has 56 divisors (see below), whose sum is σ = 152905968. Its totient is φ = 28528640.

The previous prime is 66697663. The next prime is 66697669. The reversal of 66697664 is 46679666.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66697661) 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, 9182 + ... + 14754.

Almost surely, 2^66697664 is an apocalyptic number.

66697664 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 66697664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (76452984).

66697664 is an abundant number, since it is smaller than the sum of its proper divisors (86208304).

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

66697664 is a wasteful number, since it uses less digits than its factorization.

66697664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5613 (or 5603 counting only the distinct ones).

The product of its digits is 1959552, while the sum is 50.

The square root of 66697664 is about 8166.8637799341. The cubic root of 66697664 is about 405.5429673150.

The spelling of 66697664 in words is "sixty-six million, six hundred ninety-seven thousand, six hundred sixty-four".