20163991 has 2 divisors, whose sum is σ = 20163992. Its totient is φ = 20163990.

The previous prime is 20163931. The next prime is 20164003. The reversal of 20163991 is 19936102.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20163991 - 2⁷ = 20163863 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20163911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10081995 + 10081996.

It is an arithmetic number, because the mean of its divisors is an integer number (10081996).

Almost surely, 2^20163991 is an apocalyptic number.

20163991 is a deficient number, since it is larger than the sum of its proper divisors (1).

20163991 is an equidigital number, since it uses as much as digits as its factorization.

20163991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2916, while the sum is 31.

The square root of 20163991 is about 4490.4332753087. The cubic root of 20163991 is about 272.1816431963.

It can be divided in two parts, 2016399 and 1, that added together give a square (2016400 = 1420²).

The spelling of 20163991 in words is "twenty million, one hundred sixty-three thousand, nine hundred ninety-one".