21212115 has 16 divisors (see below), whose sum is σ = 34729728. Its totient is φ = 11049696.

The previous prime is 21212111. The next prime is 21212119. The reversal of 21212115 is 51121212.

It is an interprime number because it is at equal distance from previous prime (21212111) and next prime (21212119).

It is not a de Polignac number, because 21212115 - 2² = 21212111 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 = 21212094 and 21212103.

It is not an unprimeable number, because it can be changed into a prime (21212111) 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, 15799 + ... + 17088.

It is an arithmetic number, because the mean of its divisors is an integer number (2170608).

Almost surely, 2^21212115 is an apocalyptic number.

21212115 is a deficient number, since it is larger than the sum of its proper divisors (13517613).

21212115 is a wasteful number, since it uses less digits than its factorization.

21212115 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32938.

The product of its digits is 40, while the sum is 15.

The square root of 21212115 is about 4605.6611903178. The cubic root of 21212115 is about 276.8182110361.

21212115 divided by its sum of digits (15) gives a palindrome (1414141).

Adding to 21212115 its reverse (51121212), we get a palindrome (72333327).

The spelling of 21212115 in words is "twenty-one million, two hundred twelve thousand, one hundred fifteen".