1389178781 has 2 divisors, whose sum is σ = 1389178782. Its totient is φ = 1389178780.

The previous prime is 1389178751. The next prime is 1389178837. The reversal of 1389178781 is 1878719831.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1241434756 + 147744025 = 35234^2 + 12155^2 .

It is a cyclic number.

It is not a de Polignac number, because 1389178781 - 2¹⁸ = 1388916637 is a prime.

It is a super-2 number, since 2×1389178781² = 3859635371161291922, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1389178741) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 694589390 + 694589391.

It is an arithmetic number, because the mean of its divisors is an integer number (694589391).

Almost surely, 2^1389178781 is an apocalyptic number.

It is an amenable number.

1389178781 is a deficient number, since it is larger than the sum of its proper divisors (1).

1389178781 is an equidigital number, since it uses as much as digits as its factorization.

1389178781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 677376, while the sum is 53.

The square root of 1389178781 is about 37271.6887328707. The cubic root of 1389178781 is about 1115.7992034027.

The spelling of 1389178781 in words is "one billion, three hundred eighty-nine million, one hundred seventy-eight thousand, seven hundred eighty-one".