21100021221 has 16 divisors (see below), whose sum is σ = 29359921536. Its totient is φ = 13453541376.

The previous prime is 21100021157. The next prime is 21100021249. The reversal of 21100021221 is 12212000112.

It is not a de Polignac number, because 21100021221 - 2⁶ = 21100021157 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21100021197 and 21100021206.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21100021021) 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, 1096741 + ... + 1115813.

It is an arithmetic number, because the mean of its divisors is an integer number (1834995096).

Almost surely, 2^21100021221 is an apocalyptic number.

It is an amenable number.

21100021221 is a deficient number, since it is larger than the sum of its proper divisors (8259900315).

21100021221 is a wasteful number, since it uses less digits than its factorization.

21100021221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35132.

The product of its (nonzero) digits is 16, while the sum is 12.

Adding to 21100021221 its reverse (12212000112), we get a palindrome (33312021333).

It can be divided in two parts, 211000 and 21221, that added together give a triangular number (232221 = T₆₈₁).

The spelling of 21100021221 in words is "twenty-one billion, one hundred million, twenty-one thousand, two hundred twenty-one".