21002111001 has 10 divisors (see below), whose sum is σ = 31373523962. Its totient is φ = 14001407280.

The previous prime is 21002110973. The next prime is 21002111021. The reversal of 21002111001 is 10011120012.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 15864662025 + 5137448976 = 125955^2 + 71676^2 .

It is not a de Polignac number, because 21002111001 - 2⁶ = 21002110937 is a prime.

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

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21002111021) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 129642580 + ... + 129642741.

Almost surely, 2^21002111001 is an apocalyptic number.

It is an amenable number.

21002111001 is a deficient number, since it is larger than the sum of its proper divisors (10371412961).

21002111001 is an equidigital number, since it uses as much as digits as its factorization.

21002111001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 259285333 (or 259285324 counting only the distinct ones).

The product of its (nonzero) digits is 4, while the sum is 9.

Adding to 21002111001 its reverse (10011120012), we get a palindrome (31013231013).

The spelling of 21002111001 in words is "twenty-one billion, two million, one hundred eleven thousand, one".