20561040 has 200 divisors, whose sum is σ = 75620160. Its totient is φ = 5163264.

The previous prime is 20561033. The next prime is 20561053. The reversal of 20561040 is 4016502.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 123037 + ... + 123203.

Almost surely, 2^20561040 is an apocalyptic number.

20561040 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20561040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37810080).

20561040 is an abundant number, since it is smaller than the sum of its proper divisors (55059120).

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

20561040 is a wasteful number, since it uses less digits than its factorization.

20561040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 211 (or 196 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 20561040 is about 4534.4282991354. The cubic root of 20561040 is about 273.9565526862.

Adding to 20561040 its reverse (4016502), we get a palindrome (24577542).

The spelling of 20561040 in words is "twenty million, five hundred sixty-one thousand, forty".