20257639 has 4 divisors (see below), whose sum is σ = 20301856. Its totient is φ = 20213424.

The previous prime is 20257621. The next prime is 20257669. The reversal of 20257639 is 93675202.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 20257639 - 2¹¹ = 20255591 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20257619) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 21414 + ... + 22339.

It is an arithmetic number, because the mean of its divisors is an integer number (5075464).

Almost surely, 2^20257639 is an apocalyptic number.

20257639 is a deficient number, since it is larger than the sum of its proper divisors (44217).

20257639 is an equidigital number, since it uses as much as digits as its factorization.

20257639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 44216.

The product of its (nonzero) digits is 22680, while the sum is 34.

The square root of 20257639 is about 4500.8486977458. The cubic root of 20257639 is about 272.6023586510.

The spelling of 20257639 in words is "twenty million, two hundred fifty-seven thousand, six hundred thirty-nine".