1278409399 has 2 divisors, whose sum is σ = 1278409400. Its totient is φ = 1278409398.

The previous prime is 1278409339. The next prime is 1278409423. The reversal of 1278409399 is 9939048721.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 1278409399 - 2¹⁹ = 1277885111 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1278409339) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 639204699 + 639204700.

It is an arithmetic number, because the mean of its divisors is an integer number (639204700).

Almost surely, 2^1278409399 is an apocalyptic number.

1278409399 is a deficient number, since it is larger than the sum of its proper divisors (1).

1278409399 is an equidigital number, since it uses as much as digits as its factorization.

1278409399 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 979776, while the sum is 52.

The square root of 1278409399 is about 35754.8514050891. The cubic root of 1278409399 is about 1085.3171148646.

The spelling of 1278409399 in words is "one billion, two hundred seventy-eight million, four hundred nine thousand, three hundred ninety-nine".