20505251 has 8 divisors (see below), whose sum is σ = 22139040. Its totient is φ = 18879552.

The previous prime is 20505241. The next prime is 20505253. The reversal of 20505251 is 15250502.

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-20505251 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20505253) 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, 3911 + ... + 7503.

It is an arithmetic number, because the mean of its divisors is an integer number (2767380).

Almost surely, 2^20505251 is an apocalyptic number.

20505251 is a deficient number, since it is larger than the sum of its proper divisors (1633789).

20505251 is a wasteful number, since it uses less digits than its factorization.

20505251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4045.

The product of its (nonzero) digits is 500, while the sum is 20.

The square root of 20505251 is about 4528.2724078836. The cubic root of 20505251 is about 273.7085495645.

Adding to 20505251 its reverse (15250502), we get a palindrome (35755753).

The spelling of 20505251 in words is "twenty million, five hundred five thousand, two hundred fifty-one".