20861389 has 2 divisors, whose sum is σ = 20861390. Its totient is φ = 20861388.

The previous prime is 20861371. The next prime is 20861413. The reversal of 20861389 is 98316802.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 10989225 + 9872164 = 3315^2 + 3142^2 .

It is a cyclic number.

It is not a de Polignac number, because 20861389 - 2¹¹ = 20859341 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20861339) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10430694 + 10430695.

It is an arithmetic number, because the mean of its divisors is an integer number (10430695).

Almost surely, 2^20861389 is an apocalyptic number.

It is an amenable number.

20861389 is a deficient number, since it is larger than the sum of its proper divisors (1).

20861389 is an equidigital number, since it uses as much as digits as its factorization.

20861389 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 20736, while the sum is 37.

The square root of 20861389 is about 4567.4269561757. The cubic root of 20861389 is about 275.2840656974.

The spelling of 20861389 in words is "twenty million, eight hundred sixty-one thousand, three hundred eighty-nine".