21261216613560 has 128 divisors (see below), whose sum is σ = 79522472563200. Its totient is φ = 4417915138560.

The previous prime is 21261216613531. The next prime is 21261216613597. The reversal of 21261216613560 is 6531661216212.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1150489495 + ... + 1150507974.

It is an arithmetic number, because the mean of its divisors is an integer number (621269316900).

Almost surely, 2^{21261216613560} is an apocalyptic number.

21261216613560 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21261216613560 is an abundant number, since it is smaller than the sum of its proper divisors (58261255949640).

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

21261216613560 is a wasteful number, since it uses less digits than its factorization.

21261216613560 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2300997501 (or 2300997497 counting only the distinct ones).

The product of its (nonzero) digits is 155520, while the sum is 42.

Adding to 21261216613560 its reverse (6531661216212), we get a palindrome (27792877829772).

The spelling of 21261216613560 in words is "twenty-one trillion, two hundred sixty-one billion, two hundred sixteen million, six hundred thirteen thousand, five hundred sixty".