21512121603 has 32 divisors (see below), whose sum is σ = 33244231680. Its totient is φ = 12119721600.

The previous prime is 21512121583. The next prime is 21512121607. The reversal of 21512121603 is 30612121512.

It is a happy number.

It is not a de Polignac number, because 21512121603 - 2¹⁶ = 21512056067 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21512121607) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 485701 + ... + 528137.

It is an arithmetic number, because the mean of its divisors is an integer number (1038882240).

Almost surely, 2^21512121603 is an apocalyptic number.

21512121603 is a deficient number, since it is larger than the sum of its proper divisors (11732110077).

21512121603 is a wasteful number, since it uses less digits than its factorization.

21512121603 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42787.

The product of its (nonzero) digits is 720, while the sum is 24.

Subtracting 21512121603 from its reverse (30612121512), we obtain a palindrome (9099999909).

The spelling of 21512121603 in words is "twenty-one billion, five hundred twelve million, one hundred twenty-one thousand, six hundred three".