21106844640 has 576 divisors, whose sum is σ = 87253770240. Its totient is φ = 4538695680.

The previous prime is 21106844609. The next prime is 21106844653. The reversal of 21106844640 is 4644860112.

It is a happy number.

21106844640 is a `hidden beast` number, since 2 + 1 + 1 + 0 + 6 + 8 + 4 + 4 + 640 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 21106844595 and 21106844604.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 36580032 + ... + 36580608.

It is an arithmetic number, because the mean of its divisors is an integer number (151482240).

Almost surely, 2^21106844640 is an apocalyptic number.

21106844640 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 21106844640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (43626885120).

21106844640 is an abundant number, since it is smaller than the sum of its proper divisors (66146925600).

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

21106844640 is a wasteful number, since it uses less digits than its factorization.

21106844640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 815 (or 804 counting only the distinct ones).

The product of its (nonzero) digits is 36864, while the sum is 36.

The spelling of 21106844640 in words is "twenty-one billion, one hundred six million, eight hundred forty-four thousand, six hundred forty".