20940561 has 12 divisors (see below), whose sum is σ = 30662788. Its totient is φ = 13768704.

The previous prime is 20940551. The next prime is 20940599. The reversal of 20940561 is 16504902.

It can be written as a sum of positive squares in 2 ways, for example, as 8088336 + 12852225 = 2844^2 + 3585^2 .

It is not a de Polignac number, because 20940561 - 2⁶ = 20940497 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20940551) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 15280 + ... + 16593.

Almost surely, 2^20940561 is an apocalyptic number.

It is an amenable number.

20940561 is a deficient number, since it is larger than the sum of its proper divisors (9722227).

20940561 is a wasteful number, since it uses less digits than its factorization.

20940561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31952 (or 31949 counting only the distinct ones).

The product of its (nonzero) digits is 2160, while the sum is 27.

The square root of 20940561 is about 4576.0857727975. The cubic root of 20940561 is about 275.6318737391.

The spelling of 20940561 in words is "twenty million, nine hundred forty thousand, five hundred sixty-one".