21666154400 has 144 divisors (see below), whose sum is σ = 57815674560. Its totient is φ = 7862937600.

The previous prime is 21666154387. The next prime is 21666154409. The reversal of 21666154400 is 445166612.

It is not an unprimeable number, because it can be changed into a prime (21666154409) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 5005037 + ... + 5009363.

It is an arithmetic number, because the mean of its divisors is an integer number (401497740).

Almost surely, 2^21666154400 is an apocalyptic number.

21666154400 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 21666154400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28907837280).

21666154400 is an abundant number, since it is smaller than the sum of its proper divisors (36149520160).

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

21666154400 is a wasteful number, since it uses less digits than its factorization.

21666154400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4927 (or 4914 counting only the distinct ones).

The product of its (nonzero) digits is 34560, while the sum is 35.

The spelling of 21666154400 in words is "twenty-one billion, six hundred sixty-six million, one hundred fifty-four thousand, four hundred".