21000121002 has 72 divisors (see below), whose sum is σ = 52959756096. Its totient is φ = 5996534544.

The previous prime is 21000120971. The next prime is 21000121031. The reversal of 21000121002 is 20012100012.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 1760703 + ... + 1772589.

It is an arithmetic number, because the mean of its divisors is an integer number (735552168).

Almost surely, 2^21000121002 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21000121002, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26479878048).

21000121002 is an abundant number, since it is smaller than the sum of its proper divisors (31959635094).

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

21000121002 is a wasteful number, since it uses less digits than its factorization.

21000121002 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13912 (or 13902 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 9.

Adding to 21000121002 its reverse (20012100012), we get a palindrome (41012221014).

The spelling of 21000121002 in words is "twenty-one billion, one hundred twenty-one thousand, two".