20561400 has 72 divisors (see below), whose sum is σ = 69058080. Its totient is φ = 5482560.

The previous prime is 20561369. The next prime is 20561407. The reversal of 20561400 is 416502.

It is a happy number.

20561400 is a `hidden beast` number, since 205 + 61 + 400 = 666.

It is a tau number, because it is divible by the number of its divisors (72).

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20561407) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 3912 + ... + 7511.

It is an arithmetic number, because the mean of its divisors is an integer number (959140).

Almost surely, 2^20561400 is an apocalyptic number.

20561400 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20561400 is an abundant number, since it is smaller than the sum of its proper divisors (48496680).

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

20561400 is a wasteful number, since it uses less digits than its factorization.

20561400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11445 (or 11433 counting only the distinct ones).

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

The square root of 20561400 is about 4534.4679952559. The cubic root of 20561400 is about 273.9581515642.

Adding to 20561400 its reverse (416502), we get a palindrome (20977902).

The spelling of 20561400 in words is "twenty million, five hundred sixty-one thousand, four hundred".