21001111220121 has 32 divisors (see below), whose sum is σ = 29137166069760. Its totient is φ = 13444892265600.

The previous prime is 21001111220107. The next prime is 21001111220153. The reversal of 21001111220121 is 12102211110012.

It is a happy number.

It is not a de Polignac number, because 21001111220121 - 2⁹ = 21001111219609 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21001111220121.

It is not an unprimeable number, because it can be changed into a prime (21001111221121) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1028781 + ... + 6562058.

It is an arithmetic number, because the mean of its divisors is an integer number (910536439680).

Almost surely, 2^{21001111220121} is an apocalyptic number.

It is an amenable number.

21001111220121 is a deficient number, since it is larger than the sum of its proper divisors (8136054849639).

21001111220121 is a wasteful number, since it uses less digits than its factorization.

21001111220121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7591237.

The product of its (nonzero) digits is 16, while the sum is 15.

Adding to 21001111220121 its reverse (12102211110012), we get a palindrome (33103322330133).

The spelling of 21001111220121 in words is "twenty-one trillion, one billion, one hundred eleven million, two hundred twenty thousand, one hundred twenty-one".