21881388121 has 4 divisors (see below), whose sum is σ = 21975299892. Its totient is φ = 21787476352.

The previous prime is 21881388097. The next prime is 21881388149. The reversal of 21881388121 is 12188318812.

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 5747307721 + 16134080400 = 75811^2 + 127020^2 .

It is a cyclic number.

It is not a de Polignac number, because 21881388121 - 2¹³ = 21881379929 is a prime.

It is a super-2 number, since 2×21881388121² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21881388421) 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, 46955536 + ... + 46956001.

It is an arithmetic number, because the mean of its divisors is an integer number (5493824973).

Almost surely, 2^21881388121 is an apocalyptic number.

It is an amenable number.

21881388121 is a deficient number, since it is larger than the sum of its proper divisors (93911771).

21881388121 is an equidigital number, since it uses as much as digits as its factorization.

21881388121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 93911770.

The product of its digits is 49152, while the sum is 43.

The spelling of 21881388121 in words is "twenty-one billion, eight hundred eighty-one million, three hundred eighty-eight thousand, one hundred twenty-one".