21668261580 has 864 divisors, whose sum is σ = 85886760960. Its totient is φ = 4389396480.

The previous prime is 21668261539. The next prime is 21668261581. The reversal of 21668261580 is 8516286612.

21668261580 is a `hidden beast` number, since 2 + 1 + 6 + 6 + 8 + 2 + 61 + 580 = 666.

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

It is not an unprimeable number, because it can be changed into a prime (21668261581) by changing a digit.

It is a polite number, since it can be written in 287 ways as a sum of consecutive naturals, for example, 223384092 + ... + 223384188.

Almost surely, 2^21668261580 is an apocalyptic number.

21668261580 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 21668261580, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (42943380480).

21668261580 is an abundant number, since it is smaller than the sum of its proper divisors (64218499380).

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

21668261580 is a wasteful number, since it uses less digits than its factorization.

21668261580 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 219 (or 207 counting only the distinct ones).

The product of its (nonzero) digits is 276480, while the sum is 45.

The spelling of 21668261580 in words is "twenty-one billion, six hundred sixty-eight million, two hundred sixty-one thousand, five hundred eighty".