21111221001001 has 4 divisors (see below), whose sum is σ = 21114494572500. Its totient is φ = 21107947429504.

The previous prime is 21111221000993. The next prime is 21111221001049. The reversal of 21111221001001 is 10010012211112.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 10492747041001 + 10618473960000 = 3239251^2 + 3258600^2 .

It is a cyclic number.

It is not a de Polignac number, because 21111221001001 - 2³ = 21111221000993 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21111221001401) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1636776076 + ... + 1636788973.

It is an arithmetic number, because the mean of its divisors is an integer number (5278623643125).

Almost surely, 2^{21111221001001} is an apocalyptic number.

It is an amenable number.

21111221001001 is a deficient number, since it is larger than the sum of its proper divisors (3273571499).

21111221001001 is an equidigital number, since it uses as much as digits as its factorization.

21111221001001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3273571498.

The product of its (nonzero) digits is 8, while the sum is 13.

Adding to 21111221001001 its reverse (10010012211112), we get a palindrome (31121233212113).

The spelling of 21111221001001 in words is "twenty-one trillion, one hundred eleven billion, two hundred twenty-one million, one thousand, one".