21389615 has 16 divisors (see below), whose sum is σ = 27904800. Its totient is φ = 15645312.

The previous prime is 21389593. The next prime is 21389629. The reversal of 21389615 is 51698312.

It is a cyclic number.

It is not a de Polignac number, because 21389615 - 2⁸ = 21389359 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5576 + ... + 8594.

It is an arithmetic number, because the mean of its divisors is an integer number (1744050).

Almost surely, 2^21389615 is an apocalyptic number.

21389615 is a deficient number, since it is larger than the sum of its proper divisors (6515185).

21389615 is a wasteful number, since it uses less digits than its factorization.

21389615 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3146.

The product of its digits is 12960, while the sum is 35.

The square root of 21389615 is about 4624.8908095219. The cubic root of 21389615 is about 277.5881926215.

The spelling of 21389615 in words is "twenty-one million, three hundred eighty-nine thousand, six hundred fifteen".