21539998 has 4 divisors (see below), whose sum is σ = 32310000. Its totient is φ = 10769998.

The previous prime is 21539993. The next prime is 21540017. The reversal of 21539998 is 89993512.

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 (21539993) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5384998 + ... + 5385001.

It is an arithmetic number, because the mean of its divisors is an integer number (8077500).

Almost surely, 2^21539998 is an apocalyptic number.

21539998 is a deficient number, since it is larger than the sum of its proper divisors (10770002).

21539998 is a wasteful number, since it uses less digits than its factorization.

21539998 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10770001.

The product of its digits is 174960, while the sum is 46.

The square root of 21539998 is about 4641.1203388837. The cubic root of 21539998 is about 278.2372162250.

The spelling of 21539998 in words is "twenty-one million, five hundred thirty-nine thousand, nine hundred ninety-eight".