21001001000 has 256 divisors, whose sum is σ = 62059944960. Its totient is φ = 6481305600.

The previous prime is 21001000991. The next prime is 21001001009. The reversal of 21001001000 is 10010012.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21001000991) and next prime (21001001009).

It is a Harshad number since it is a multiple of its sum of digits (5).

It is not an unprimeable number, because it can be changed into a prime (21001001009) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 2733164 + ... + 2740836.

It is an arithmetic number, because the mean of its divisors is an integer number (242421660).

Almost surely, 2^21001001000 is an apocalyptic number.

21001001000 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 21001001000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31029972480).

21001001000 is an abundant number, since it is smaller than the sum of its proper divisors (41058943960).

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

21001001000 is a wasteful number, since it uses less digits than its factorization.

21001001000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7741 (or 7727 counting only the distinct ones).

The product of its (nonzero) digits is 2, while the sum is 5.

Adding to 21001001000 its reverse (10010012), we get a palindrome (21011011012).

The spelling of 21001001000 in words is "twenty-one billion, one million, one thousand".