2638670821 has 4 divisors (see below), whose sum is σ = 2729659500. Its totient is φ = 2547682144.

The previous prime is 2638670819. The next prime is 2638670869. The reversal of 2638670821 is 1280768362.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1280768362 = 2 ⋅640384181.

It can be written as a sum of positive squares in 2 ways, for example, as 823058721 + 1815612100 = 28689^2 + 42610^2 .

It is a cyclic number.

It is not a de Polignac number, because 2638670821 - 2¹ = 2638670819 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 (2638670621) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 45494296 + ... + 45494353.

It is an arithmetic number, because the mean of its divisors is an integer number (682414875).

Almost surely, 2^2638670821 is an apocalyptic number.

It is an amenable number.

2638670821 is a deficient number, since it is larger than the sum of its proper divisors (90988679).

2638670821 is an equidigital number, since it uses as much as digits as its factorization.

2638670821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 90988678.

The product of its (nonzero) digits is 193536, while the sum is 43.

The square root of 2638670821 is about 51367.9941305868. The cubic root of 2638670821 is about 1381.8526578361.

The spelling of 2638670821 in words is "two billion, six hundred thirty-eight million, six hundred seventy thousand, eight hundred twenty-one".