1278487421 has 2 divisors, whose sum is σ = 1278487422. Its totient is φ = 1278487420.

The previous prime is 1278487393. The next prime is 1278487477. The reversal of 1278487421 is 1247848721.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 748843225 + 529644196 = 27365^2 + 23014^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1278487421 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1278487921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 639243710 + 639243711.

It is an arithmetic number, because the mean of its divisors is an integer number (639243711).

Almost surely, 2^1278487421 is an apocalyptic number.

It is an amenable number.

1278487421 is a deficient number, since it is larger than the sum of its proper divisors (1).

1278487421 is an equidigital number, since it uses as much as digits as its factorization.

1278487421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 200704, while the sum is 44.

The square root of 1278487421 is about 35755.9424571637. The cubic root of 1278487421 is about 1085.3391935741.

The spelling of 1278487421 in words is "one billion, two hundred seventy-eight million, four hundred eighty-seven thousand, four hundred twenty-one".