66640690 has 8 divisors (see below), whose sum is σ = 119953260. Its totient is φ = 26656272.

The previous prime is 66640667. The next prime is 66640699. The reversal of 66640690 is 9604666.

It can be written as a sum of positive squares in 2 ways, for example, as 65658609 + 982081 = 8103^2 + 991^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-2 number, since 2×66640690² = 8881963127352200, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (66640699) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3332025 + ... + 3332044.

Almost surely, 2^66640690 is an apocalyptic number.

66640690 is a deficient number, since it is larger than the sum of its proper divisors (53312570).

66640690 is a wasteful number, since it uses less digits than its factorization.

66640690 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6664076.

The product of its (nonzero) digits is 46656, while the sum is 37.

The square root of 66640690 is about 8163.3749148254. The cubic root of 66640690 is about 405.4274610851.

The spelling of 66640690 in words is "sixty-six million, six hundred forty thousand, six hundred ninety".