1257999991 has 2 divisors, whose sum is σ = 1257999992. Its totient is φ = 1257999990.

The previous prime is 1257999989. The next prime is 1258000049. The reversal of 1257999991 is 1999997521.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1257999991 - 2¹ = 1257999989 is a prime.

Together with 1257999989, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1257999931) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 628999995 + 628999996.

It is an arithmetic number, because the mean of its divisors is an integer number (628999996).

Almost surely, 2^1257999991 is an apocalyptic number.

1257999991 is a deficient number, since it is larger than the sum of its proper divisors (1).

1257999991 is an equidigital number, since it uses as much as digits as its factorization.

1257999991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4133430, while the sum is 61.

The square root of 1257999991 is about 35468.2955750625. The cubic root of 1257999991 is about 1079.5105209323.

The spelling of 1257999991 in words is "one billion, two hundred fifty-seven million, nine hundred ninety-nine thousand, nine hundred ninety-one".