21520646 has 16 divisors (see below), whose sum is σ = 36954144. Its totient is φ = 9207744.

The previous prime is 21520637. The next prime is 21520649. The reversal of 21520646 is 64602512.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21520649) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12536 + ... + 14148.

It is an arithmetic number, because the mean of its divisors is an integer number (2309634).

Almost surely, 2^21520646 is an apocalyptic number.

21520646 is a deficient number, since it is larger than the sum of its proper divisors (15433498).

21520646 is a wasteful number, since it uses less digits than its factorization.

21520646 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2575.

The product of its (nonzero) digits is 2880, while the sum is 26.

The square root of 21520646 is about 4639.0350289688. The cubic root of 21520646 is about 278.1538664816.

The spelling of 21520646 in words is "twenty-one million, five hundred twenty thousand, six hundred forty-six".