6391779421 has 2 divisors, whose sum is σ = 6391779422. Its totient is φ = 6391779420.

The previous prime is 6391779413. The next prime is 6391779439. The reversal of 6391779421 is 1249771936.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 4954611321 + 1437168100 = 70389^2 + 37910^2 .

It is a cyclic number.

It is not a de Polignac number, because 6391779421 - 2³ = 6391779413 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (6691779421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3195889710 + 3195889711.

It is an arithmetic number, because the mean of its divisors is an integer number (3195889711).

Almost surely, 2^6391779421 is an apocalyptic number.

It is an amenable number.

6391779421 is a deficient number, since it is larger than the sum of its proper divisors (1).

6391779421 is an equidigital number, since it uses as much as digits as its factorization.

6391779421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 571536, while the sum is 49.

The square root of 6391779421 is about 79948.6048721302. The cubic root of 6391779421 is about 1855.8402647726.

The spelling of 6391779421 in words is "six billion, three hundred ninety-one million, seven hundred seventy-nine thousand, four hundred twenty-one".