291191021 has 4 divisors (see below), whose sum is σ = 317662944. Its totient is φ = 264719100.

The previous prime is 291191009. The next prime is 291191057. The reversal of 291191021 is 120191192.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 291191021 - 2¹⁸ = 290928877 is a prime.

It is a super-2 number, since 2×291191021² = 169584421422044882, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (291191071) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13235945 + ... + 13235966.

It is an arithmetic number, because the mean of its divisors is an integer number (79415736).

Almost surely, 2^291191021 is an apocalyptic number.

It is an amenable number.

291191021 is a deficient number, since it is larger than the sum of its proper divisors (26471923).

291191021 is a wasteful number, since it uses less digits than its factorization.

291191021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26471922.

The product of its (nonzero) digits is 324, while the sum is 26.

The square root of 291191021 is about 17064.3201153752. The cubic root of 291191021 is about 662.8155058740.

The spelling of 291191021 in words is "two hundred ninety-one million, one hundred ninety-one thousand, twenty-one".