21001221221111 has 4 divisors (see below), whose sum is σ = 22236587175312. Its totient is φ = 19765855266912.

The previous prime is 21001221221041. The next prime is 21001221221147. The reversal of 21001221221111 is 11112212210012.

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

It is a cyclic number.

It is not a de Polignac number, because 21001221221111 - 2²² = 21001217026807 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (17), and also a Moran number because the ratio is a prime number: 1235365954183 = 21001221221111 / (2 + 1 + 0 + 0 + 1 + 2 + 2 + 1 + 2 + 2 + 1 + 1 + 1 + 1).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21001221221111.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001221223111) 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, 617682977075 + ... + 617682977108.

It is an arithmetic number, because the mean of its divisors is an integer number (5559146793828).

Almost surely, 2^{21001221221111} is an apocalyptic number.

21001221221111 is a deficient number, since it is larger than the sum of its proper divisors (1235365954201).

21001221221111 is a wasteful number, since it uses less digits than its factorization.

21001221221111 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1235365954200.

The product of its (nonzero) digits is 32, while the sum is 17.

Adding to 21001221221111 its reverse (11112212210012), we get a palindrome (32113433431123).

It can be divided in two parts, 2100122 and 1221111, that added together give a palindrome (3321233).

The spelling of 21001221221111 in words is "twenty-one trillion, one billion, two hundred twenty-one million, two hundred twenty-one thousand, one hundred eleven".