21015240015 has 32 divisors (see below), whose sum is σ = 41921312256. Its totient is φ = 8733605760.

The previous prime is 21015239969. The next prime is 21015240041. The reversal of 21015240015 is 51004251012.

It is not a de Polignac number, because 21015240015 - 2¹⁰ = 21015238991 is a prime.

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

It is a junction number, because it is equal to n+sod(n) for n = 21015239973 and 21015240000.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 9096352 + ... + 9098661.

It is an arithmetic number, because the mean of its divisors is an integer number (1310041008).

Almost surely, 2^21015240015 is an apocalyptic number.

21015240015 is a deficient number, since it is larger than the sum of its proper divisors (20906072241).

21015240015 is a wasteful number, since it uses less digits than its factorization.

21015240015 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18195039.

The product of its (nonzero) digits is 400, while the sum is 21.

Adding to 21015240015 its reverse (51004251012), we get a palindrome (72019491027).

The spelling of 21015240015 in words is "twenty-one billion, fifteen million, two hundred forty thousand, fifteen".