21013615 has 16 divisors (see below), whose sum is σ = 30514752. Its totient is φ = 13561344.

The previous prime is 21013609. The next prime is 21013621. The reversal of 21013615 is 51631012.

It is an interprime number because it is at equal distance from previous prime (21013609) and next prime (21013621).

It is a cyclic number.

It is not a de Polignac number, because 21013615 - 2⁵ = 21013583 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21013592 and 21013601.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 17064 + ... + 18253.

It is an arithmetic number, because the mean of its divisors is an integer number (1907172).

Almost surely, 2^21013615 is an apocalyptic number.

21013615 is a deficient number, since it is larger than the sum of its proper divisors (9501137).

21013615 is a wasteful number, since it uses less digits than its factorization.

21013615 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 35346.

The product of its (nonzero) digits is 180, while the sum is 19.

The square root of 21013615 is about 4584.0609725439. The cubic root of 21013615 is about 275.9520281744.

Adding to 21013615 its reverse (51631012), we get a palindrome (72644627).

The spelling of 21013615 in words is "twenty-one million, thirteen thousand, six hundred fifteen".