20091691 has 2 divisors, whose sum is σ = 20091692. Its totient is φ = 20091690.

The previous prime is 20091679. The next prime is 20091697. The reversal of 20091691 is 19619002.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20091691 - 2⁹ = 20091179 is a prime.

It is not a weakly prime, because it can be changed into another prime (20091697) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10045845 + 10045846.

It is an arithmetic number, because the mean of its divisors is an integer number (10045846).

Almost surely, 2^20091691 is an apocalyptic number.

20091691 is a deficient number, since it is larger than the sum of its proper divisors (1).

20091691 is an equidigital number, since it uses as much as digits as its factorization.

20091691 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 972, while the sum is 28.

The square root of 20091691 is about 4482.3755978276. The cubic root of 20091691 is about 271.8559421353.

The spelling of 20091691 in words is "twenty million, ninety-one thousand, six hundred ninety-one".