21111128640 has 840 divisors, whose sum is σ = 87901564608. Its totient is φ = 4646799360.

The previous prime is 21111128617. The next prime is 21111128653. The reversal of 21111128640 is 4682111112.

It is a happy number.

21111128640 is a `hidden beast` number, since 2 + 1 + 1 + 1 + 1 + 12 + 8 + 640 = 666.

It is a tau number, because it is divible by the number of its divisors (840).

It is an unprimeable number.

It is a polite number, since it can be written in 119 ways as a sum of consecutive naturals, for example, 297339805 + ... + 297339875.

Almost surely, 2^21111128640 is an apocalyptic number.

21111128640 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 21111128640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (43950782304).

21111128640 is an abundant number, since it is smaller than the sum of its proper divisors (66790435968).

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

21111128640 is an equidigital number, since it uses as much as digits as its factorization.

21111128640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 165 (or 131 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 27.

Adding to 21111128640 its reverse (4682111112), we get a palindrome (25793239752).

The spelling of 21111128640 in words is "twenty-one billion, one hundred eleven million, one hundred twenty-eight thousand, six hundred forty".