21539679 has 16 divisors (see below), whose sum is σ = 32904960. Its totient is φ = 12277440.

The previous prime is 21539671. The next prime is 21539681. The reversal of 21539679 is 97693512.

It is not a de Polignac number, because 21539679 - 2³ = 21539671 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21539679.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21539671) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 9267 + ... + 11355.

It is an arithmetic number, because the mean of its divisors is an integer number (2056560).

Almost surely, 2^21539679 is an apocalyptic number.

21539679 is a deficient number, since it is larger than the sum of its proper divisors (11365281).

21539679 is a wasteful number, since it uses less digits than its factorization.

21539679 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2590.

The product of its digits is 102060, while the sum is 42.

The square root of 21539679 is about 4641.0859720544. The cubic root of 21539679 is about 278.2358426855.

The spelling of 21539679 in words is "twenty-one million, five hundred thirty-nine thousand, six hundred seventy-nine".