21011001001 has 2 divisors, whose sum is σ = 21011001002. Its totient is φ = 21011001000.

The previous prime is 21011000987. The next prime is 21011001049. The reversal of 21011001001 is 10010011012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18032461225 + 2978539776 = 134285^2 + 54576^2 .

It is a cyclic number.

It is not a de Polignac number, because 21011001001 - 2¹³ = 21010992809 is a prime.

It is a super-4 number, since 4×21011001001⁴ (a number of 42 digits) contains 4444 as substring.

It is not a weakly prime, because it can be changed into another prime (21011001071) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10505500500 + 10505500501.

It is an arithmetic number, because the mean of its divisors is an integer number (10505500501).

Almost surely, 2^21011001001 is an apocalyptic number.

It is an amenable number.

21011001001 is a deficient number, since it is larger than the sum of its proper divisors (1).

21011001001 is an equidigital number, since it uses as much as digits as its factorization.

21011001001 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2, while the sum is 7.

Adding to 21011001001 its reverse (10010011012), we get a palindrome (31021012013).

The spelling of 21011001001 in words is "twenty-one billion, eleven million, one thousand, one".