20521657 has 8 divisors (see below), whose sum is σ = 22571136. Its totient is φ = 18539472.

The previous prime is 20521651. The next prime is 20521661. The reversal of 20521657 is 75612502.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20521657 is a prime.

It is a super-2 number, since 2×20521657² = 842276812051298, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20521651) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 16183 + ... + 17404.

It is an arithmetic number, because the mean of its divisors is an integer number (2821392).

Almost surely, 2^20521657 is an apocalyptic number.

It is an amenable number.

20521657 is a deficient number, since it is larger than the sum of its proper divisors (2049479).

20521657 is a wasteful number, since it uses less digits than its factorization.

20521657 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33647.

The product of its (nonzero) digits is 4200, while the sum is 28.

The square root of 20521657 is about 4530.0835533133. The cubic root of 20521657 is about 273.7815270571.

The spelling of 20521657 in words is "twenty million, five hundred twenty-one thousand, six hundred fifty-seven".