21161072121 has 16 divisors (see below), whose sum is σ = 32289100800. Its totient is φ = 12075669648.

The previous prime is 21161072117. The next prime is 21161072137. The reversal of 21161072121 is 12127016112.

It is not a de Polignac number, because 21161072121 - 2² = 21161072117 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21161072091 and 21161072100.

It is not an unprimeable number, because it can be changed into a prime (21160072121) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 666261 + ... + 697298.

It is an arithmetic number, because the mean of its divisors is an integer number (2018068800).

Almost surely, 2^21161072121 is an apocalyptic number.

21161072121 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21161072121 is a deficient number, since it is larger than the sum of its proper divisors (11128028679).

21161072121 is a wasteful number, since it uses less digits than its factorization.

21161072121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1364308.

The product of its (nonzero) digits is 336, while the sum is 24.

Adding to 21161072121 its reverse (12127016112), we get a palindrome (33288088233).

The spelling of 21161072121 in words is "twenty-one billion, one hundred sixty-one million, seventy-two thousand, one hundred twenty-one".