1666623509 has 8 divisors (see below), whose sum is σ = 1767100608. Its totient is φ = 1566417600.

The previous prime is 1666623481. The next prime is 1666623659. The reversal of 1666623509 is 9053266661.

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 1666623509 - 2¹⁶ = 1666557973 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 1666623509.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1666623109) 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, 55067 + ... + 79784.

It is an arithmetic number, because the mean of its divisors is an integer number (220887576).

Almost surely, 2^1666623509 is an apocalyptic number.

It is an amenable number.

1666623509 is a deficient number, since it is larger than the sum of its proper divisors (100477099).

1666623509 is a wasteful number, since it uses less digits than its factorization.

1666623509 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 135595.

The product of its (nonzero) digits is 349920, while the sum is 44.

The square root of 1666623509 is about 40824.3004716554. The cubic root of 1666623509 is about 1185.6208675940.

The spelling of 1666623509 in words is "one billion, six hundred sixty-six million, six hundred twenty-three thousand, five hundred nine".