21978188144640 has 2688 divisors, whose sum is σ = 98226030136320. Its totient is φ = 4564558282752.

The previous prime is 21978188144611. The next prime is 21978188144681. The reversal of 21978188144640 is 4644188187912.

21978188144640 is a `hidden beast` number, since 2 + 1 + 9 + 7 + 8 + 188 + 1 + 446 + 4 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (2688).

It is a Harshad number since it is a multiple of its sum of digits (63).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 191 ways as a sum of consecutive naturals, for example, 139988459442 + ... + 139988459598.

Almost surely, 2^{21978188144640} is an apocalyptic number.

21978188144640 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 21978188144640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (49113015068160).

21978188144640 is an abundant number, since it is smaller than the sum of its proper divisors (76247841991680).

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

21978188144640 is a wasteful number, since it uses less digits than its factorization.

21978188144640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 337 (or 294 counting only the distinct ones).

The product of its (nonzero) digits is 24772608, while the sum is 63.

The spelling of 21978188144640 in words is "twenty-one trillion, nine hundred seventy-eight billion, one hundred eighty-eight million, one hundred forty-four thousand, six hundred forty".