21221010121 has 4 divisors (see below), whose sum is σ = 22469304852. Its totient is φ = 19972715392.

The previous prime is 21221010113. The next prime is 21221010131. The reversal of 21221010121 is 12101012212.

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

It can be written as a sum of positive squares in 2 ways, for example, as 10931748025 + 10289262096 = 104555^2 + 101436^2 .

It is a cyclic number.

It is not a de Polignac number, because 21221010121 - 2³ = 21221010113 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21221010131) 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, 624147340 + ... + 624147373.

It is an arithmetic number, because the mean of its divisors is an integer number (5617326213).

Almost surely, 2^21221010121 is an apocalyptic number.

It is an amenable number.

21221010121 is a deficient number, since it is larger than the sum of its proper divisors (1248294731).

21221010121 is a wasteful number, since it uses less digits than its factorization.

21221010121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1248294730.

The product of its (nonzero) digits is 16, while the sum is 13.

Adding to 21221010121 its reverse (12101012212), we get a palindrome (33322022333).

The spelling of 21221010121 in words is "twenty-one billion, two hundred twenty-one million, ten thousand, one hundred twenty-one".