21042515 has 32 divisors (see below), whose sum is σ = 29211840. Its totient is φ = 14413824.

The previous prime is 21042491. The next prime is 21042533. The reversal of 21042515 is 51524012.

It is not a de Polignac number, because 21042515 - 2¹² = 21038419 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 151316 + ... + 151454.

It is an arithmetic number, because the mean of its divisors is an integer number (912870).

Almost surely, 2^21042515 is an apocalyptic number.

21042515 is a deficient number, since it is larger than the sum of its proper divisors (8169325).

21042515 is a wasteful number, since it uses less digits than its factorization.

21042515 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 311.

The product of its (nonzero) digits is 400, while the sum is 20.

The square root of 21042515 is about 4587.2121163077. The cubic root of 21042515 is about 276.0784757243.

Adding to 21042515 its reverse (51524012), we get a palindrome (72566527).

The spelling of 21042515 in words is "twenty-one million, forty-two thousand, five hundred fifteen".