21005168553 has 24 divisors (see below), whose sum is σ = 33038990400. Its totient is φ = 12808956384.

The previous prime is 21005168551. The next prime is 21005168603. The reversal of 21005168553 is 35586150012.

It is a happy number.

21005168553 is a `hidden beast` number, since 2 + 10 + 0 + 516 + 85 + 53 = 666.

It is not a de Polignac number, because 21005168553 - 2¹ = 21005168551 is a prime.

It is a super-2 number, since 2×21005168553² (a number of 21 digits) contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21005168551) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2112925 + ... + 2122842.

It is an arithmetic number, because the mean of its divisors is an integer number (1376624600).

Almost surely, 2^21005168553 is an apocalyptic number.

It is an amenable number.

21005168553 is a deficient number, since it is larger than the sum of its proper divisors (12033821847).

21005168553 is a wasteful number, since it uses less digits than its factorization.

21005168553 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4235821 (or 4235818 counting only the distinct ones).

The product of its (nonzero) digits is 36000, while the sum is 36.

The spelling of 21005168553 in words is "twenty-one billion, five million, one hundred sixty-eight thousand, five hundred fifty-three".