21520605 has 8 divisors (see below), whose sum is σ = 34432992. Its totient is φ = 11477648.

The previous prime is 21520573. The next prime is 21520607. The reversal of 21520605 is 50602512.

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 21520605 - 2⁵ = 21520573 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21520607) 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 7 ways as a sum of consecutive naturals, for example, 717339 + ... + 717368.

It is an arithmetic number, because the mean of its divisors is an integer number (4304124).

Almost surely, 2^21520605 is an apocalyptic number.

It is an amenable number.

21520605 is a deficient number, since it is larger than the sum of its proper divisors (12912387).

21520605 is a wasteful number, since it uses less digits than its factorization.

21520605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1434715.

The product of its (nonzero) digits is 600, while the sum is 21.

The square root of 21520605 is about 4639.0306099443. The cubic root of 21520605 is about 278.1536898401.

The spelling of 21520605 in words is "twenty-one million, five hundred twenty thousand, six hundred five".