20561418 has 64 divisors (see below), whose sum is σ = 48263040. Its totient is φ = 6480000.

The previous prime is 20561417. The next prime is 20561423. The reversal of 20561418 is 81416502.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a junction number, because it is equal to n+sod(n) for n = 20561391 and 20561400.

It is not an unprimeable number, because it can be changed into a prime (20561413) 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 31 ways as a sum of consecutive naturals, for example, 81793 + ... + 82043.

It is an arithmetic number, because the mean of its divisors is an integer number (754110).

Almost surely, 2^20561418 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20561418, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24131520).

20561418 is an abundant number, since it is smaller than the sum of its proper divisors (27701622).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

20561418 is a wasteful number, since it uses less digits than its factorization.

20561418 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 340 (or 334 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 27.

The square root of 20561418 is about 4534.4699800528. The cubic root of 20561418 is about 273.9582315077.

The spelling of 20561418 in words is "twenty million, five hundred sixty-one thousand, four hundred eighteen".