1391959981 has 2 divisors, whose sum is σ = 1391959982. Its totient is φ = 1391959980.

The previous prime is 1391959973. The next prime is 1391960029. The reversal of 1391959981 is 1899591931.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1241505225 + 150454756 = 35235^2 + 12266^2 .

It is a cyclic number.

It is not a de Polignac number, because 1391959981 - 2³ = 1391959973 is a prime.

It is a super-2 number, since 2×1391959981² = 3875105177411040722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1391959901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 695979990 + 695979991.

It is an arithmetic number, because the mean of its divisors is an integer number (695979991).

Almost surely, 2^1391959981 is an apocalyptic number.

It is an amenable number.

1391959981 is a deficient number, since it is larger than the sum of its proper divisors (1).

1391959981 is an equidigital number, since it uses as much as digits as its factorization.

1391959981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 787320, while the sum is 55.

The square root of 1391959981 is about 37308.9798976064. The cubic root of 1391959981 is about 1116.5433341870.

The spelling of 1391959981 in words is "one billion, three hundred ninety-one million, nine hundred fifty-nine thousand, nine hundred eighty-one".