2661878221 has 2 divisors, whose sum is σ = 2661878222. Its totient is φ = 2661878220.

The previous prime is 2661878119. The next prime is 2661878231. The reversal of 2661878221 is 1228781662.

It is a happy number.

2661878221 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 2448864196 + 213014025 = 49486^2 + 14595^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-2661878221 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2661878231) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1330939110 + 1330939111.

It is an arithmetic number, because the mean of its divisors is an integer number (1330939111).

Almost surely, 2^2661878221 is an apocalyptic number.

It is an amenable number.

2661878221 is a deficient number, since it is larger than the sum of its proper divisors (1).

2661878221 is an equidigital number, since it uses as much as digits as its factorization.

2661878221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 129024, while the sum is 43.

The square root of 2661878221 is about 51593.3931913767. The cubic root of 2661878221 is about 1385.8920206880.

The spelling of 2661878221 in words is "two billion, six hundred sixty-one million, eight hundred seventy-eight thousand, two hundred twenty-one".