21121153555 has 16 divisors (see below), whose sum is σ = 25538214240. Its totient is φ = 16768470528.

The previous prime is 21121153517. The next prime is 21121153561. The reversal of 21121153555 is 55535112112.

It is a cyclic number.

It is not a de Polignac number, because 21121153555 - 2⁹ = 21121153043 is a prime.

It is a super-2 number, since 2×21121153555² (a number of 21 digits) contains 22 as substring.

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 15 ways as a sum of consecutive naturals, for example, 2297949 + ... + 2307121.

It is an arithmetic number, because the mean of its divisors is an integer number (1596138390).

Almost surely, 2^21121153555 is an apocalyptic number.

21121153555 is a deficient number, since it is larger than the sum of its proper divisors (4417060685).

21121153555 is a wasteful number, since it uses less digits than its factorization.

21121153555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12630.

The product of its digits is 7500, while the sum is 31.

Adding to 21121153555 its reverse (55535112112), we get a palindrome (76656265667).

The spelling of 21121153555 in words is "twenty-one billion, one hundred twenty-one million, one hundred fifty-three thousand, five hundred fifty-five".