21356404121660 has 24 divisors (see below), whose sum is σ = 47486592694800. Its totient is φ = 8040058022144.

The previous prime is 21356404121593. The next prime is 21356404121669. The reversal of 21356404121660 is 6612140465312.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21356404121669) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 31406476310 + ... + 31406476989.

It is an arithmetic number, because the mean of its divisors is an integer number (1978608028950).

Almost surely, 2^{21356404121660} is an apocalyptic number.

21356404121660 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21356404121660 is an abundant number, since it is smaller than the sum of its proper divisors (26130188573140).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21356404121660 is a wasteful number, since it uses less digits than its factorization.

21356404121660 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 62812953325 (or 62812953323 counting only the distinct ones).

The product of its (nonzero) digits is 207360, while the sum is 41.

Adding to 21356404121660 its reverse (6612140465312), we get a palindrome (27968544586972).

The spelling of 21356404121660 in words is "twenty-one trillion, three hundred fifty-six billion, four hundred four million, one hundred twenty-one thousand, six hundred sixty".