21508634 has 16 divisors (see below), whose sum is σ = 38475648. Its totient is φ = 8817072.

The previous prime is 21508631. The next prime is 21508649. The reversal of 21508634 is 43680512.

It is a junction number, because it is equal to n+sod(n) for n = 21508597 and 21508606.

It is not an unprimeable number, because it can be changed into a prime (21508631) 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, 33077 + ... + 33720.

It is an arithmetic number, because the mean of its divisors is an integer number (2404728).

Almost surely, 2^21508634 is an apocalyptic number.

21508634 is a deficient number, since it is larger than the sum of its proper divisors (16967014).

21508634 is a wasteful number, since it uses less digits than its factorization.

21508634 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 66829.

The product of its (nonzero) digits is 5760, while the sum is 29.

The square root of 21508634 is about 4637.7401824596. The cubic root of 21508634 is about 278.1021052399.

The spelling of 21508634 in words is "twenty-one million, five hundred eight thousand, six hundred thirty-four".