1351991 has 2 divisors, whose sum is σ = 1351992. Its totient is φ = 1351990.

The previous prime is 1351981. The next prime is 1351997. The reversal of 1351991 is 1991531.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1351991 is a prime.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1351997) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 675995 + 675996.

It is an arithmetic number, because the mean of its divisors is an integer number (675996).

2^1351991 is an apocalyptic number.

1351991 is a deficient number, since it is larger than the sum of its proper divisors (1).

1351991 is an equidigital number, since it uses as much as digits as its factorization.

1351991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1215, while the sum is 29.

The square root of 1351991 is about 1162.7514781758. The cubic root of 1351991 is about 110.5752509132.

The spelling of 1351991 in words is "one million, three hundred fifty-one thousand, nine hundred ninety-one".