21001221101218 has 16 divisors (see below), whose sum is σ = 32240970137376. Its totient is φ = 10254330112320.

The previous prime is 21001221101213. The next prime is 21001221101219. The reversal of 21001221101218 is 81210112210012.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (21001221101213) 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, 24337671 + ... + 25185802.

It is an arithmetic number, because the mean of its divisors is an integer number (2015060633586).

Almost surely, 2^{21001221101218} is an apocalyptic number.

21001221101218 is a deficient number, since it is larger than the sum of its proper divisors (11239749036158).

21001221101218 is a wasteful number, since it uses less digits than its factorization.

21001221101218 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 49528449.

The product of its (nonzero) digits is 128, while the sum is 22.

The spelling of 21001221101218 in words is "twenty-one trillion, one billion, two hundred twenty-one million, one hundred one thousand, two hundred eighteen".