66640521 has 8 divisors (see below), whose sum is σ = 91918080. Its totient is φ = 42894992.

The previous prime is 66640489. The next prime is 66640531. The reversal of 66640521 is 12504666.

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

It is a cyclic number.

It is not a de Polignac number, because 66640521 - 2⁵ = 66640489 is a prime.

It is not an unprimeable number, because it can be changed into a prime (66640531) 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, 382905 + ... + 383078.

It is an arithmetic number, because the mean of its divisors is an integer number (11489760).

Almost surely, 2^66640521 is an apocalyptic number.

It is an amenable number.

66640521 is a deficient number, since it is larger than the sum of its proper divisors (25277559).

66640521 is a wasteful number, since it uses less digits than its factorization.

66640521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 766015.

The product of its (nonzero) digits is 8640, while the sum is 30.

The square root of 66640521 is about 8163.3645637078. The cubic root of 66640521 is about 405.4271183651.

It can be divided in two parts, 66640 and 521, that added together give a triangular number (67161 = T₃₆₆).

The spelling of 66640521 in words is "sixty-six million, six hundred forty thousand, five hundred twenty-one".