1665263498821 has 4 divisors (see below), whose sum is σ = 1793360691052. Its totient is φ = 1537166306592.

The previous prime is 1665263498807. The next prime is 1665263498827. The reversal of 1665263498821 is 1288943625661.

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 82294396900 + 1582969101921 = 286870^2 + 1258161^2 .

It is a cyclic number.

It is not a de Polignac number, because 1665263498821 - 2²³ = 1665255110213 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 1665263498821.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1665263498827) 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, 64048596096 + ... + 64048596121.

It is an arithmetic number, because the mean of its divisors is an integer number (448340172763).

Almost surely, 2^{1665263498821} is an apocalyptic number.

It is an amenable number.

1665263498821 is a deficient number, since it is larger than the sum of its proper divisors (128097192231).

1665263498821 is a wasteful number, since it uses less digits than its factorization.

1665263498821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 128097192230.

The product of its digits is 29859840, while the sum is 61.

The spelling of 1665263498821 in words is "one trillion, six hundred sixty-five billion, two hundred sixty-three million, four hundred ninety-eight thousand, eight hundred twenty-one".