21090015 has 12 divisors (see below), whose sum is σ = 36556104. Its totient is φ = 11247984.

The previous prime is 21090007. The next prime is 21090061. The reversal of 21090015 is 51009012.

It is not a de Polignac number, because 21090015 - 2³ = 21090007 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21090015.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 234289 + ... + 234378.

It is an arithmetic number, because the mean of its divisors is an integer number (3046342).

Almost surely, 2^21090015 is an apocalyptic number.

21090015 is a deficient number, since it is larger than the sum of its proper divisors (15466089).

21090015 is a wasteful number, since it uses less digits than its factorization.

21090015 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 468678 (or 468675 counting only the distinct ones).

The product of its (nonzero) digits is 90, while the sum is 18.

The square root of 21090015 is about 4592.3866344201. The cubic root of 21090015 is about 276.2860534560.

Adding to 21090015 its reverse (51009012), we get a palindrome (72099027).

The spelling of 21090015 in words is "twenty-one million, ninety thousand, fifteen".