21455123121 has 24 divisors (see below), whose sum is σ = 31085810184. Its totient is φ = 14259594240.

The previous prime is 21455123119. The next prime is 21455123149. The reversal of 21455123121 is 12132155412.

It is a happy number.

21455123121 is a `hidden beast` number, since 2 + 145 + 512 + 3 + 1 + 2 + 1 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 127441521 + 21327681600 = 11289^2 + 146040^2 .

It is not a de Polignac number, because 21455123121 - 2¹ = 21455123119 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21455123021) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 8788261 + ... + 8790701.

It is an arithmetic number, because the mean of its divisors is an integer number (1295242091).

Almost surely, 2^21455123121 is an apocalyptic number.

It is an amenable number.

21455123121 is a deficient number, since it is larger than the sum of its proper divisors (9630687063).

21455123121 is a wasteful number, since it uses less digits than its factorization.

21455123121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5041 (or 5038 counting only the distinct ones).

The product of its digits is 2400, while the sum is 27.

Adding to 21455123121 its reverse (12132155412), we get a palindrome (33587278533).

The spelling of 21455123121 in words is "twenty-one billion, four hundred fifty-five million, one hundred twenty-three thousand, one hundred twenty-one".