665541514021 has 4 divisors (see below), whose sum is σ = 678098901132. Its totient is φ = 652984126912.

The previous prime is 665541513979. The next prime is 665541514031. The reversal of 665541514021 is 120415145566.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 307326096900 + 358215417121 = 554370^2 + 598511^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-665541514021 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 (665541514031) 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, 6278693476 + ... + 6278693581.

It is an arithmetic number, because the mean of its divisors is an integer number (169524725283).

Almost surely, 2^665541514021 is an apocalyptic number.

It is an amenable number.

665541514021 is a deficient number, since it is larger than the sum of its proper divisors (12557387111).

665541514021 is a wasteful number, since it uses less digits than its factorization.

665541514021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12557387110.

The product of its (nonzero) digits is 144000, while the sum is 40.

Adding to 665541514021 its reverse (120415145566), we get a palindrome (785956659587).

The spelling of 665541514021 in words is "six hundred sixty-five billion, five hundred forty-one million, five hundred fourteen thousand, twenty-one".