21056615 has 16 divisors (see below), whose sum is σ = 26500608. Its totient is φ = 16031136.

The previous prime is 21056597. The next prime is 21056653. The reversal of 21056615 is 51665012.

It is a cyclic number.

It is not a de Polignac number, because 21056615 - 2⁶ = 21056551 is a prime.

It is a Duffinian number.

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, 32222 + ... + 32868.

It is an arithmetic number, because the mean of its divisors is an integer number (1656288).

Almost surely, 2^21056615 is an apocalyptic number.

21056615 is a deficient number, since it is larger than the sum of its proper divisors (5443993).

21056615 is a wasteful number, since it uses less digits than its factorization.

21056615 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 958.

The product of its (nonzero) digits is 1800, while the sum is 26.

The square root of 21056615 is about 4588.7487401251. The cubic root of 21056615 is about 276.1401261080.

The spelling of 21056615 in words is "twenty-one million, fifty-six thousand, six hundred fifteen".