21012115105 has 24 divisors (see below), whose sum is σ = 26629229952. Its totient is φ = 15914343456.

The previous prime is 21012115099. The next prime is 21012115147. The reversal of 21012115105 is 50151121012.

It is not a de Polignac number, because 21012115105 - 2¹⁵ = 21012082337 is a prime.

It is a super-2 number, since 2×21012115105² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (19).

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3655864 + ... + 3661606.

It is an arithmetic number, because the mean of its divisors is an integer number (1109551248).

Almost surely, 2^21012115105 is an apocalyptic number.

It is an amenable number.

21012115105 is a deficient number, since it is larger than the sum of its proper divisors (5617114847).

21012115105 is a wasteful number, since it uses less digits than its factorization.

21012115105 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7813 (or 7794 counting only the distinct ones).

The product of its (nonzero) digits is 100, while the sum is 19.

Adding to 21012115105 its reverse (50151121012), we get a palindrome (71163236117).

The spelling of 21012115105 in words is "twenty-one billion, twelve million, one hundred fifteen thousand, one hundred five".