21121163603565 has 96 divisors (see below), whose sum is σ = 37001109277440. Its totient is φ = 10281307545600.

The previous prime is 21121163603563. The next prime is 21121163603581. The reversal of 21121163603565 is 56530636112112.

It is a happy number.

It is not a de Polignac number, because 21121163603565 - 2¹ = 21121163603563 is a prime.

It is a super-2 number, since 2×21121163603565² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121163603563) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 18212401 + ... + 19337369.

It is an arithmetic number, because the mean of its divisors is an integer number (385428221640).

Almost surely, 2^{21121163603565} is an apocalyptic number.

It is an amenable number.

21121163603565 is a deficient number, since it is larger than the sum of its proper divisors (15879945673875).

21121163603565 is a wasteful number, since it uses less digits than its factorization.

21121163603565 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1125143 (or 1125126 counting only the distinct ones).

The product of its (nonzero) digits is 194400, while the sum is 42.

Adding to 21121163603565 its reverse (56530636112112), we get a palindrome (77651799715677).

The spelling of 21121163603565 in words is "twenty-one trillion, one hundred twenty-one billion, one hundred sixty-three million, six hundred three thousand, five hundred sixty-five".