21290215 has 4 divisors (see below), whose sum is σ = 25548264. Its totient is φ = 17032168.

The previous prime is 21290189. The next prime is 21290219. The reversal of 21290215 is 51209212.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21290215 - 2⁹ = 21289703 is a prime.

It is a Duffinian number.

It is a zygodrome in base 3.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21290219) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2129017 + ... + 2129026.

It is an arithmetic number, because the mean of its divisors is an integer number (6387066).

Almost surely, 2^21290215 is an apocalyptic number.

21290215 is a deficient number, since it is larger than the sum of its proper divisors (4258049).

21290215 is an equidigital number, since it uses as much as digits as its factorization.

21290215 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4258048.

The product of its (nonzero) digits is 360, while the sum is 22.

The square root of 21290215 is about 4614.1320960718. The cubic root of 21290215 is about 277.1575300700.

Adding to 21290215 its reverse (51209212), we get a palindrome (72499427).

The spelling of 21290215 in words is "twenty-one million, two hundred ninety thousand, two hundred fifteen".