21508118 has 4 divisors (see below), whose sum is σ = 32262180. Its totient is φ = 10754058.

The previous prime is 21508117. The next prime is 21508121. The reversal of 21508118 is 81180512.

It is a semiprime because it is the product of two primes.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21508117) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5377028 + ... + 5377031.

It is an arithmetic number, because the mean of its divisors is an integer number (8065545).

Almost surely, 2^21508118 is an apocalyptic number.

21508118 is a deficient number, since it is larger than the sum of its proper divisors (10754062).

21508118 is a wasteful number, since it uses less digits than its factorization.

21508118 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10754061.

The product of its (nonzero) digits is 640, while the sum is 26.

The square root of 21508118 is about 4637.6845515839. The cubic root of 21508118 is about 278.0998812984.

The spelling of 21508118 in words is "twenty-one million, five hundred eight thousand, one hundred eighteen".