20971997 has 2 divisors, whose sum is σ = 20971998. Its totient is φ = 20971996.

The previous prime is 20971987. The next prime is 20972023. The reversal of 20971997 is 79917902.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16048036 + 4923961 = 4006^2 + 2219^2 .

It is a cyclic number.

It is not a de Polignac number, because 20971997 - 2¹² = 20967901 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 (20971957) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10485998 + 10485999.

It is an arithmetic number, because the mean of its divisors is an integer number (10485999).

Almost surely, 2^20971997 is an apocalyptic number.

It is an amenable number.

20971997 is a deficient number, since it is larger than the sum of its proper divisors (1).

20971997 is an equidigital number, since it uses as much as digits as its factorization.

20971997 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 71442, while the sum is 44.

The square root of 20971997 is about 4579.5192979176. The cubic root of 20971997 is about 275.7697310987.

The spelling of 20971997 in words is "twenty million, nine hundred seventy-one thousand, nine hundred ninety-seven".