21355545121 has 4 divisors (see below), whose sum is σ = 22479521200. Its totient is φ = 20231569044.

The previous prime is 21355545119. The next prime is 21355545137. The reversal of 21355545121 is 12154555312.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21355545121 - 2¹ = 21355545119 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21355545181) 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, 561988011 + ... + 561988048.

It is an arithmetic number, because the mean of its divisors is an integer number (5619880300).

Almost surely, 2^21355545121 is an apocalyptic number.

It is an amenable number.

21355545121 is a deficient number, since it is larger than the sum of its proper divisors (1123976079).

21355545121 is a wasteful number, since it uses less digits than its factorization.

21355545121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1123976078.

The product of its digits is 30000, while the sum is 34.

The spelling of 21355545121 in words is "twenty-one billion, three hundred fifty-five million, five hundred forty-five thousand, one hundred twenty-one".