21539718 has 24 divisors (see below), whose sum is σ = 47010600. Its totient is φ = 7127424.

The previous prime is 21539717. The next prime is 21539729. The reversal of 21539718 is 81793512.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21539717) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1803 + ... + 6806.

It is an arithmetic number, because the mean of its divisors is an integer number (1958775).

Almost surely, 2^21539718 is an apocalyptic number.

21539718 is an abundant number, since it is smaller than the sum of its proper divisors (25470882).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21539718 is a wasteful number, since it uses less digits than its factorization.

21539718 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8756 (or 8753 counting only the distinct ones).

The product of its digits is 15120, while the sum is 36.

The square root of 21539718 is about 4641.0901736553. The cubic root of 21539718 is about 278.2360106111.

The spelling of 21539718 in words is "twenty-one million, five hundred thirty-nine thousand, seven hundred eighteen".