21515134421 has 16 divisors (see below), whose sum is σ = 24786639360. Its totient is φ = 18483387120.

The previous prime is 21515134357. The next prime is 21515134429. The reversal of 21515134421 is 12443151512.

It is a happy number.

It is not a de Polignac number, because 21515134421 - 2⁶ = 21515134357 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21515134429) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 491291 + ... + 533288.

It is an arithmetic number, because the mean of its divisors is an integer number (1549164960).

Almost surely, 2^21515134421 is an apocalyptic number.

It is an amenable number.

21515134421 is a deficient number, since it is larger than the sum of its proper divisors (3271504939).

21515134421 is a wasteful number, since it uses less digits than its factorization.

21515134421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1024696.

The product of its digits is 4800, while the sum is 29.

Adding to 21515134421 its reverse (12443151512), we get a palindrome (33958285933).

The spelling of 21515134421 in words is "twenty-one billion, five hundred fifteen million, one hundred thirty-four thousand, four hundred twenty-one".