21213015 has 16 divisors (see below), whose sum is σ = 35417088. Its totient is φ = 10821536.

The previous prime is 21213013. The next prime is 21213029. The reversal of 21213015 is 51031212.

It is a cyclic number.

It is not a de Polignac number, because 21213015 - 2¹ = 21213013 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 = 21212985 and 21213003.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21213011) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 30399 + ... + 31088.

It is an arithmetic number, because the mean of its divisors is an integer number (2213568).

Almost surely, 2^21213015 is an apocalyptic number.

21213015 is a deficient number, since it is larger than the sum of its proper divisors (14204073).

21213015 is a wasteful number, since it uses less digits than its factorization.

21213015 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 61518.

The product of its (nonzero) digits is 60, while the sum is 15.

The square root of 21213015 is about 4605.7588951225. The cubic root of 21213015 is about 276.8221259823.

Adding to 21213015 its reverse (51031212), we get a palindrome (72244227).

The spelling of 21213015 in words is "twenty-one million, two hundred thirteen thousand, fifteen".