21001212121011 has 16 divisors (see below), whose sum is σ = 29651481709344. Its totient is φ = 13176025954304.

The previous prime is 21001212120871. The next prime is 21001212121031. The reversal of 21001212121011 is 11012121210012.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 21001212121011 - 2¹⁵ = 21001212088243 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21001212121031) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 18267690 + ... + 19383263.

It is an arithmetic number, because the mean of its divisors is an integer number (1853217606834).

Almost surely, 2^{21001212121011} is an apocalyptic number.

21001212121011 is a deficient number, since it is larger than the sum of its proper divisors (8650269588333).

21001212121011 is a wasteful number, since it uses less digits than its factorization.

21001212121011 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37661910.

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

Adding to 21001212121011 its reverse (11012121210012), we get a palindrome (32013333331023).

The spelling of 21001212121011 in words is "twenty-one trillion, one billion, two hundred twelve million, one hundred twenty-one thousand, eleven".