21021012011 has 4 divisors (see below), whose sum is σ = 21024292224. Its totient is φ = 21017731800.

The previous prime is 21021011993. The next prime is 21021012029. The reversal of 21021012011 is 11021012012.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (21021011993) and next prime (21021012029).

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21021012011 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21021011983 and 21021012001.

It is not an unprimeable number, because it can be changed into a prime (21021012041) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1630475 + ... + 1643316.

It is an arithmetic number, because the mean of its divisors is an integer number (5256073056).

Almost surely, 2^21021012011 is an apocalyptic number.

21021012011 is a deficient number, since it is larger than the sum of its proper divisors (3280213).

21021012011 is an equidigital number, since it uses as much as digits as its factorization.

21021012011 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3280212.

The product of its (nonzero) digits is 8, while the sum is 11.

Adding to 21021012011 its reverse (11021012012), we get a palindrome (32042024023).

Subtracting from 21021012011 its reverse (11021012012), we obtain a palindrome (9999999999).

The spelling of 21021012011 in words is "twenty-one billion, twenty-one million, twelve thousand, eleven".