21111001000 has 64 divisors (see below), whose sum is σ = 49578731280. Its totient is φ = 8413804800.

The previous prime is 21111000997. The next prime is 21111001057. The reversal of 21111001000 is 10011112.

It can be written as a sum of positive squares in 8 ways, for example, as 113252164 + 20997748836 = 10642^2 + 144906^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 238894 + ... + 315106.

Almost surely, 2^21111001000 is an apocalyptic number.

21111001000 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 21111001000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24789365640).

21111001000 is an abundant number, since it is smaller than the sum of its proper divisors (28467730280).

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

21111001000 is a wasteful number, since it uses less digits than its factorization.

21111001000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 76511 (or 76497 counting only the distinct ones).

The product of its (nonzero) digits is 2, while the sum is 7.

Adding to 21111001000 its reverse (10011112), we get a palindrome (21121012112).

The spelling of 21111001000 in words is "twenty-one billion, one hundred eleven million, one thousand".