66551509 has 4 divisors (see below), whose sum is σ = 70054240. Its totient is φ = 63048780.

The previous prime is 66551503. The next prime is 66551519. The reversal of 66551509 is 90515566.

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 a cyclic number.

It is not a de Polignac number, because 66551509 - 2³ = 66551501 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66551501) 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, 1751337 + ... + 1751374.

It is an arithmetic number, because the mean of its divisors is an integer number (17513560).

Almost surely, 2^66551509 is an apocalyptic number.

It is an amenable number.

66551509 is a deficient number, since it is larger than the sum of its proper divisors (3502731).

66551509 is a wasteful number, since it uses less digits than its factorization.

66551509 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3502730.

The product of its (nonzero) digits is 40500, while the sum is 37.

The square root of 66551509 is about 8157.9108232439. The cubic root of 66551509 is about 405.2465277493.

The spelling of 66551509 in words is "sixty-six million, five hundred fifty-one thousand, five hundred nine".