21679505 has 8 divisors (see below), whose sum is σ = 27545832. Its totient is φ = 16323328.

The previous prime is 21679477. The next prime is 21679561. The reversal of 21679505 is 50597612.

It can be written as a sum of positive squares in 4 ways, for example, as 5607424 + 16072081 = 2368^2 + 4009^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21679505 - 2⁸ = 21679249 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 127442 + ... + 127611.

It is an arithmetic number, because the mean of its divisors is an integer number (3443229).

Almost surely, 2^21679505 is an apocalyptic number.

It is an amenable number.

21679505 is a deficient number, since it is larger than the sum of its proper divisors (5866327).

21679505 is a wasteful number, since it uses less digits than its factorization.

21679505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 255075.

The product of its (nonzero) digits is 18900, while the sum is 35.

The square root of 21679505 is about 4656.1255352492. The cubic root of 21679505 is about 278.8366056379.

The spelling of 21679505 in words is "twenty-one million, six hundred seventy-nine thousand, five hundred five".