21081281177 has 4 divisors (see below), whose sum is σ = 22997761296. Its totient is φ = 19164801060.

The previous prime is 21081281173. The next prime is 21081281191. The reversal of 21081281177 is 77118218012.

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 21081281177 - 2² = 21081281173 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21081281177.

It is not an unprimeable number, because it can be changed into a prime (21081281173) 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, 958240043 + ... + 958240064.

It is an arithmetic number, because the mean of its divisors is an integer number (5749440324).

Almost surely, 2^21081281177 is an apocalyptic number.

It is an amenable number.

21081281177 is a deficient number, since it is larger than the sum of its proper divisors (1916480119).

21081281177 is a wasteful number, since it uses less digits than its factorization.

21081281177 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1916480118.

The product of its (nonzero) digits is 12544, while the sum is 38.

Adding to 21081281177 its reverse (77118218012), we get a palindrome (98199499189).

The spelling of 21081281177 in words is "twenty-one billion, eighty-one million, two hundred eighty-one thousand, one hundred seventy-seven".