21506416 has 10 divisors (see below), whose sum is σ = 41668712. Its totient is φ = 10753200.

The previous prime is 21506389. The next prime is 21506417. The reversal of 21506416 is 61460512.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21506417) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 672060 + ... + 672091.

Almost surely, 2^21506416 is an apocalyptic number.

It is an amenable number.

21506416 is a deficient number, since it is larger than the sum of its proper divisors (20162296).

21506416 is a wasteful number, since it uses less digits than its factorization.

21506416 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1344159 (or 1344153 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 25.

The square root of 21506416 is about 4637.5010512128. The cubic root of 21506416 is about 278.0925454871.

Adding to 21506416 its reverse (61460512), we get a palindrome (82966928).

The spelling of 21506416 in words is "twenty-one million, five hundred six thousand, four hundred sixteen".