642251 has 4 divisors (see below), whose sum is σ = 644400. Its totient is φ = 640104.

The previous prime is 642247. The next prime is 642253. The reversal of 642251 is 152246.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 152246 = 2 ⋅76123.

It is a cyclic number.

It is not a de Polignac number, because 642251 - 2² = 642247 is a prime.

It is a Duffinian number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 642251.

It is not an unprimeable number, because it can be changed into a prime (642253) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 536 + ... + 1253.

It is an arithmetic number, because the mean of its divisors is an integer number (161100).

2⁶⁴²²⁵¹ is an apocalyptic number.

642251 is a deficient number, since it is larger than the sum of its proper divisors (2149).

642251 is a wasteful number, since it uses less digits than its factorization.

642251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2148.

The product of its digits is 480, while the sum is 20.

The square root of 642251 is about 801.4056401099. The cubic root of 642251 is about 86.2783033905.

Adding to 642251 its reverse (152246), we get a palindrome (794497).

The spelling of 642251 in words is "six hundred forty-two thousand, two hundred fifty-one".