6561667620 has 36 divisors (see below), whose sum is σ = 19903725660. Its totient is φ = 1749777984.

The previous prime is 6561667559. The next prime is 6561667643. The reversal of 6561667620 is 267661656.

6561667620 is a `hidden beast` number, since 6 + 5 + 6 + 16 + 6 + 7 + 620 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 4851679716 + 1709987904 = 69654^2 + 41352^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 18226675 + ... + 18227034.

Almost surely, 2^6561667620 is an apocalyptic number.

6561667620 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

6561667620 is an abundant number, since it is smaller than the sum of its proper divisors (13342058040).

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

6561667620 is a wasteful number, since it uses less digits than its factorization.

6561667620 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36453724 (or 36453719 counting only the distinct ones).

The product of its (nonzero) digits is 544320, while the sum is 45.

The square root of 6561667620 is about 81004.1210062797. The cubic root of 6561667620 is about 1872.1389367898.

The spelling of 6561667620 in words is "six billion, five hundred sixty-one million, six hundred sixty-seven thousand, six hundred twenty".