66691644 has 24 divisors (see below), whose sum is σ = 156737280. Its totient is φ = 22070064.

The previous prime is 66691643. The next prime is 66691657. The reversal of 66691644 is 44619666.

It is a junction number, because it is equal to n+sod(n) for n = 66691596 and 66691605.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66691643) 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, 18324 + ... + 21659.

It is an arithmetic number, because the mean of its divisors is an integer number (6530720).

Almost surely, 2^66691644 is an apocalyptic number.

It is an amenable number.

66691644 is an abundant number, since it is smaller than the sum of its proper divisors (90045636).

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

66691644 is a wasteful number, since it uses less digits than its factorization.

66691644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40129 (or 40127 counting only the distinct ones).

The product of its digits is 186624, while the sum is 42.

The square root of 66691644 is about 8166.4952090845. The cubic root of 66691644 is about 405.5307657776.

The spelling of 66691644 in words is "sixty-six million, six hundred ninety-one thousand, six hundred forty-four".