66649521 has 4 divisors (see below), whose sum is σ = 88866032. Its totient is φ = 44433012.

The previous prime is 66649489. The next prime is 66649529. The reversal of 66649521 is 12594666.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 66649521 - 2⁵ = 66649489 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 66649521.

It is not an unprimeable number, because it can be changed into a prime (66649529) 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, 11108251 + ... + 11108256.

It is an arithmetic number, because the mean of its divisors is an integer number (22216508).

Almost surely, 2^66649521 is an apocalyptic number.

It is an amenable number.

66649521 is a deficient number, since it is larger than the sum of its proper divisors (22216511).

66649521 is a wasteful number, since it uses less digits than its factorization.

66649521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22216510.

The product of its digits is 77760, while the sum is 39.

The square root of 66649521 is about 8163.9157883947. The cubic root of 66649521 is about 405.4453689218.

The spelling of 66649521 in words is "sixty-six million, six hundred forty-nine thousand, five hundred twenty-one".