66957921 has 28 divisors (see below), whose sum is σ = 102344148. Its totient is φ = 43771104.

The previous prime is 66957907. The next prime is 66957929. The reversal of 66957921 is 12975966.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 39237696 + 27720225 = 6264^2 + 5265^2 .

It is not a de Polignac number, because 66957921 - 2¹⁷ = 66826849 is a prime.

It is a zygodrome in base 3.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66957929) by changing a digit.

It is a polite number, since it can be written in 27 ways as a sum of consecutive naturals, for example, 37771 + ... + 39503.

Almost surely, 2^66957921 is an apocalyptic number.

It is an amenable number.

66957921 is a deficient number, since it is larger than the sum of its proper divisors (35386227).

66957921 is an equidigital number, since it uses as much as digits as its factorization.

66957921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1804 (or 1789 counting only the distinct ones).

The product of its digits is 204120, while the sum is 45.

The square root of 66957921 is about 8182.7819841421. The cubic root of 66957921 is about 406.0697644357.

The spelling of 66957921 in words is "sixty-six million, nine hundred fifty-seven thousand, nine hundred twenty-one".