21651821270640 has 1200 divisors, whose sum is σ = 89377532614656. Its totient is φ = 4812081177600.

The previous prime is 21651821270623. The next prime is 21651821270647. The reversal of 21651821270640 is 4607212815612.

21651821270640 is a `hidden beast` number, since 2 + 1 + 6 + 518 + 2 + 1 + 2 + 70 + 64 + 0 = 666.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21651821270647) by changing a digit.

It is a polite number, since it can be written in 239 ways as a sum of consecutive naturals, for example, 797680909 + ... + 797708051.

Almost surely, 2^{21651821270640} is an apocalyptic number.

21651821270640 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 21651821270640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (44688766307328).

21651821270640 is an abundant number, since it is smaller than the sum of its proper divisors (67725711344016).

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

21651821270640 is a wasteful number, since it uses less digits than its factorization.

21651821270640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27248 (or 27214 counting only the distinct ones).

The product of its (nonzero) digits is 322560, while the sum is 45.

The spelling of 21651821270640 in words is "twenty-one trillion, six hundred fifty-one billion, eight hundred twenty-one million, two hundred seventy thousand, six hundred forty".