21201212111111 has 8 divisors (see below), whose sum is σ = 22452580265760. Its totient is φ = 19950314848768.

The previous prime is 21201212111041. The next prime is 21201212111117. The reversal of 21201212111111 is 11111121210212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21201212111111 - 2¹⁰ = 21201212110087 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (17).

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 21201212111111.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21201212111117) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 117630371 + ... + 117810468.

It is an arithmetic number, because the mean of its divisors is an integer number (2806572533220).

Almost surely, 2^{21201212111111} is an apocalyptic number.

21201212111111 is a deficient number, since it is larger than the sum of its proper divisors (1251368154649).

21201212111111 is a wasteful number, since it uses less digits than its factorization.

21201212111111 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 235446153.

The product of its (nonzero) digits is 16, while the sum is 17.

Adding to 21201212111111 its reverse (11111121210212), we get a palindrome (32312333321323).

The spelling of 21201212111111 in words is "twenty-one trillion, two hundred one billion, two hundred twelve million, one hundred eleven thousand, one hundred eleven".