6616781 has 2 divisors, whose sum is σ = 6616782. Its totient is φ = 6616780.

The previous prime is 6616777. The next prime is 6616783. The reversal of 6616781 is 1876166.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 6604900 + 11881 = 2570^2 + 109^2 .

It is a cyclic number.

It is not a de Polignac number, because 6616781 - 2² = 6616777 is a prime.

It is a super-2 number, since 2×6616781² = 87563581603922, which contains 22 as substring.

Together with 6616783, it forms a pair of twin primes.

It is a Chen prime.

It is an Ulam number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6616783) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3308390 + 3308391.

It is an arithmetic number, because the mean of its divisors is an integer number (3308391).

Almost surely, 2^6616781 is an apocalyptic number.

It is an amenable number.

6616781 is a deficient number, since it is larger than the sum of its proper divisors (1).

6616781 is an equidigital number, since it uses as much as digits as its factorization.

6616781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12096, while the sum is 35.

The square root of 6616781 is about 2572.3104400519. The cubic root of 6616781 is about 187.7365878659.

The spelling of 6616781 in words is "six million, six hundred sixteen thousand, seven hundred eighty-one".