21420015 has 32 divisors (see below), whose sum is σ = 36550656. Its totient is φ = 10686720.

The previous prime is 21420013. The next prime is 21420023. The reversal of 21420015 is 51002412.

It is not a de Polignac number, because 21420015 - 2¹ = 21420013 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a junction number, because it is equal to n+sod(n) for n = 21419976 and 21420003.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21420013) 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 31 ways as a sum of consecutive naturals, for example, 15555 + ... + 16875.

It is an arithmetic number, because the mean of its divisors is an integer number (1142208).

Almost surely, 2^21420015 is an apocalyptic number.

21420015 is a deficient number, since it is larger than the sum of its proper divisors (15130641).

21420015 is a wasteful number, since it uses less digits than its factorization.

21420015 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1399.

The product of its (nonzero) digits is 80, while the sum is 15.

The square root of 21420015 is about 4628.1762066715. The cubic root of 21420015 is about 277.7196378171.

Adding to 21420015 its reverse (51002412), we get a palindrome (72422427).

The spelling of 21420015 in words is "twenty-one million, four hundred twenty thousand, fifteen".