21001021011 has 16 divisors (see below), whose sum is σ = 31506457600. Its totient is φ = 13823455464.

The previous prime is 21001021003. The next prime is 21001021049. The reversal of 21001021011 is 11012010012.

It is a happy number.

It is not a de Polignac number, because 21001021011 - 2³ = 21001021003 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 a junction number, because it is equal to n+sod(n) for n = 21001020984 and 21001021002.

It is not an unprimeable number, because it can be changed into a prime (21001021061) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4920751 + ... + 4925016.

It is an arithmetic number, because the mean of its divisors is an integer number (1969153600).

Almost surely, 2^21001021011 is an apocalyptic number.

21001021011 is a deficient number, since it is larger than the sum of its proper divisors (10505436589).

21001021011 is an equidigital number, since it uses as much as digits as its factorization.

21001021011 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9845855 (or 9845849 counting only the distinct ones).

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

Adding to 21001021011 its reverse (11012010012), we get a palindrome (32013031023).

The spelling of 21001021011 in words is "twenty-one billion, one million, twenty-one thousand, eleven".