20861549 has 2 divisors, whose sum is σ = 20861550. Its totient is φ = 20861548.

The previous prime is 20861539. The next prime is 20861557. The reversal of 20861549 is 94516802.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16933225 + 3928324 = 4115^2 + 1982^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20861549 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 (20861509) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10430774 + 10430775.

It is an arithmetic number, because the mean of its divisors is an integer number (10430775).

Almost surely, 2^20861549 is an apocalyptic number.

It is an amenable number.

20861549 is a deficient number, since it is larger than the sum of its proper divisors (1).

20861549 is an equidigital number, since it uses as much as digits as its factorization.

20861549 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 17280, while the sum is 35.

The square root of 20861549 is about 4567.4444714742. Note that the first 4 decimals coincide. The cubic root of 20861549 is about 275.2847694750.

The spelling of 20861549 in words is "twenty million, eight hundred sixty-one thousand, five hundred forty-nine".