20717521 has 16 divisors (see below), whose sum is σ = 23474880. Its totient is φ = 18118080.

The previous prime is 20717497. The next prime is 20717527. The reversal of 20717521 is 12571702.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 20717521 - 2¹¹ = 20715473 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20717527) 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, 44130 + ... + 44596.

It is an arithmetic number, because the mean of its divisors is an integer number (1467180).

Almost surely, 2^20717521 is an apocalyptic number.

It is an amenable number.

20717521 is a deficient number, since it is larger than the sum of its proper divisors (2757359).

20717521 is a wasteful number, since it uses less digits than its factorization.

20717521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 624.

The product of its (nonzero) digits is 980, while the sum is 25.

The square root of 20717521 is about 4551.6503600343. The cubic root of 20717521 is about 274.6497844891.

The spelling of 20717521 in words is "twenty million, seven hundred seventeen thousand, five hundred twenty-one".