21520535 has 4 divisors (see below), whose sum is σ = 25824648. Its totient is φ = 17216424.

The previous prime is 21520529. The next prime is 21520537. The reversal of 21520535 is 53502512.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21520535 - 2⁴ = 21520519 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21520535.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21520537) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2152049 + ... + 2152058.

It is an arithmetic number, because the mean of its divisors is an integer number (6456162).

Almost surely, 2^21520535 is an apocalyptic number.

21520535 is a deficient number, since it is larger than the sum of its proper divisors (4304113).

21520535 is an equidigital number, since it uses as much as digits as its factorization.

21520535 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4304112.

The product of its (nonzero) digits is 1500, while the sum is 23.

The square root of 21520535 is about 4639.0230652585. The cubic root of 21520535 is about 278.1533882566.

The spelling of 21520535 in words is "twenty-one million, five hundred twenty thousand, five hundred thirty-five".