2666398333921 has 27 divisors (see below), whose sum is σ = 3114613100529. Its totient is φ = 2276029731528.

The previous prime is 2666398333919. The next prime is 2666398333933. The reversal of 2666398333921 is 1293338936662.

It is a happy number.

The square root of 2666398333921 is 1632911.

It is a perfect power (a square), and thus also a powerful number.

It is not a de Polignac number, because 2666398333921 - 2¹ = 2666398333919 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 2666398333921.

It is not an unprimeable number, because it can be changed into a prime (2666398333121) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 5475150340 + ... + 5475150826.

Almost surely, 2^{2666398333921} is an apocalyptic number.

2666398333921 is the 1632911-st square number.

2666398333921 is the 816456-th centered octagonal number.

It is an amenable number.

2666398333921 is a deficient number, since it is larger than the sum of its proper divisors (448214766608).

2666398333921 is an frugal number, since it uses more digits than its factorization.

2666398333921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1946 (or 973 counting only the distinct ones).

The product of its digits is 45349632, while the sum is 61.

The spelling of 2666398333921 in words is "two trillion, six hundred sixty-six billion, three hundred ninety-eight million, three hundred thirty-three thousand, nine hundred twenty-one".