6721861 has 2 divisors, whose sum is σ = 6721862. Its totient is φ = 6721860.

The previous prime is 6721859. The next prime is 6721867. The reversal of 6721861 is 1681276.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 5317636 + 1404225 = 2306^2 + 1185^2 .

It is a cyclic number.

It is not a de Polignac number, because 6721861 - 2¹ = 6721859 is a prime.

Together with 6721859, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6721867) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3360930 + 3360931.

It is an arithmetic number, because the mean of its divisors is an integer number (3360931).

Almost surely, 2^6721861 is an apocalyptic number.

It is an amenable number.

6721861 is a deficient number, since it is larger than the sum of its proper divisors (1).

6721861 is an equidigital number, since it uses as much as digits as its factorization.

6721861 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4032, while the sum is 31.

The square root of 6721861 is about 2592.6552026831. The cubic root of 6721861 is about 188.7251775027.

The spelling of 6721861 in words is "six million, seven hundred twenty-one thousand, eight hundred sixty-one".