6561500400 has 360 divisors, whose sum is σ = 28026296480. Its totient is φ = 1384335360.

The previous prime is 6561500383. The next prime is 6561500401. The reversal of 6561500400 is 40051656.

It is a happy number.

6561500400 is a `hidden beast` number, since 6 + 5 + 615 + 0 + 0 + 40 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (360).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (6561500401) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 317586 + ... + 337614.

Almost surely, 2^6561500400 is an apocalyptic number.

6561500400 is a gapful number since it is divisible by the number (60) 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 6561500400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (14013148240).

6561500400 is an abundant number, since it is smaller than the sum of its proper divisors (21464796080).

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

6561500400 is a wasteful number, since it uses less digits than its factorization.

6561500400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20073 (or 20059 counting only the distinct ones).

The product of its (nonzero) digits is 3600, while the sum is 27.

The square root of 6561500400 is about 81003.0888299946. The cubic root of 6561500400 is about 1872.1230332243.

The spelling of 6561500400 in words is "six billion, five hundred sixty-one million, five hundred thousand, four hundred".