20897861 has 2 divisors, whose sum is σ = 20897862. Its totient is φ = 20897860.

The previous prime is 20897857. The next prime is 20897867. The reversal of 20897861 is 16879802.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18541636 + 2356225 = 4306^2 + 1535^2 .

It is a cyclic number.

It is not a de Polignac number, because 20897861 - 2² = 20897857 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20897867) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10448930 + 10448931.

It is an arithmetic number, because the mean of its divisors is an integer number (10448931).

Almost surely, 2^20897861 is an apocalyptic number.

It is an amenable number.

20897861 is a deficient number, since it is larger than the sum of its proper divisors (1).

20897861 is an equidigital number, since it uses as much as digits as its factorization.

20897861 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 48384, while the sum is 41.

The square root of 20897861 is about 4571.4178325767. The cubic root of 20897861 is about 275.4443988219. Note that the first 3 decimals are identical.

The spelling of 20897861 in words is "twenty million, eight hundred ninety-seven thousand, eight hundred sixty-one".