291521997391 has 2 divisors, whose sum is σ = 291521997392. Its totient is φ = 291521997390.

The previous prime is 291521997359. The next prime is 291521997409. The reversal of 291521997391 is 193799125192.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 291521997391 - 2⁵ = 291521997359 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (291521997331) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 145760998695 + 145760998696.

It is an arithmetic number, because the mean of its divisors is an integer number (145760998696).

Almost surely, 2^291521997391 is an apocalyptic number.

291521997391 is a deficient number, since it is larger than the sum of its proper divisors (1).

291521997391 is an equidigital number, since it uses as much as digits as its factorization.

291521997391 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2755620, while the sum is 58.

The spelling of 291521997391 in words is "two hundred ninety-one billion, five hundred twenty-one million, nine hundred ninety-seven thousand, three hundred ninety-one".