21005102055 has 64 divisors (see below), whose sum is σ = 39594147840. Its totient is φ = 9309961344.

The previous prime is 21005102039. The next prime is 21005102059. The reversal of 21005102055 is 55020150012.

It is not a de Polignac number, because 21005102055 - 2⁴ = 21005102039 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21005102059) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 508156 + ... + 547934.

It is an arithmetic number, because the mean of its divisors is an integer number (618658560).

Almost surely, 2^21005102055 is an apocalyptic number.

21005102055 is a deficient number, since it is larger than the sum of its proper divisors (18589045785).

21005102055 is a wasteful number, since it uses less digits than its factorization.

21005102055 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39948.

The product of its (nonzero) digits is 500, while the sum is 21.

Adding to 21005102055 its reverse (55020150012), we get a palindrome (76025252067).

The spelling of 21005102055 in words is "twenty-one billion, five million, one hundred two thousand, fifty-five".