21654656478 has 360 divisors, whose sum is σ = 63577335888. Its totient is φ = 5393246976.

The previous prime is 21654656477. The next prime is 21654656479. The reversal of 21654656478 is 87465645612.

21654656478 is a `hidden beast` number, since 2 + 1 + 6 + 5 + 4 + 6 + 564 + 78 = 666.

It is an interprime number because it is at equal distance from previous prime (21654656477) and next prime (21654656479).

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21654656477) by changing a digit.

It is a polite number, since it can be written in 179 ways as a sum of consecutive naturals, for example, 69184050 + ... + 69184362.

Almost surely, 2^21654656478 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21654656478, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31788667944).

21654656478 is an abundant number, since it is smaller than the sum of its proper divisors (41922679410).

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

21654656478 is a wasteful number, since it uses less digits than its factorization.

21654656478 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 398 (or 357 counting only the distinct ones).

The product of its digits is 9676800, while the sum is 54.

The spelling of 21654656478 in words is "twenty-one billion, six hundred fifty-four million, six hundred fifty-six thousand, four hundred seventy-eight".