20391251 has 8 divisors (see below), whose sum is σ = 20624208. Its totient is φ = 20160000.

The previous prime is 20391229. The next prime is 20391257. The reversal of 20391251 is 15219302.

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-20391251 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20391257) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 50651 + ... + 51051.

It is an arithmetic number, because the mean of its divisors is an integer number (2578026).

Almost surely, 2^20391251 is an apocalyptic number.

20391251 is a deficient number, since it is larger than the sum of its proper divisors (232957).

20391251 is a wasteful number, since it uses less digits than its factorization.

20391251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 853.

The product of its (nonzero) digits is 540, while the sum is 23.

The square root of 20391251 is about 4515.6672818090. The cubic root of 20391251 is about 273.2003743920.

The spelling of 20391251 in words is "twenty million, three hundred ninety-one thousand, two hundred fifty-one".