20891197 has 2 divisors, whose sum is σ = 20891198. Its totient is φ = 20891196.

The previous prime is 20891161. The next prime is 20891209. The reversal of 20891197 is 79119802.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17884441 + 3006756 = 4229^2 + 1734^2 .

It is a cyclic number.

It is not a de Polignac number, because 20891197 - 2¹⁵ = 20858429 is a prime.

It is a super-2 number, since 2×20891197² = 872884224185618, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20891597) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10445598 + 10445599.

It is an arithmetic number, because the mean of its divisors is an integer number (10445599).

Almost surely, 2^20891197 is an apocalyptic number.

It is an amenable number.

20891197 is a deficient number, since it is larger than the sum of its proper divisors (1).

20891197 is an equidigital number, since it uses as much as digits as its factorization.

20891197 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 9072, while the sum is 37.

The square root of 20891197 is about 4570.6888977483. The cubic root of 20891197 is about 275.4151174102.

The spelling of 20891197 in words is "twenty million, eight hundred ninety-one thousand, one hundred ninety-seven".