20781253 has 4 divisors (see below), whose sum is σ = 21451648. Its totient is φ = 20110860.

The previous prime is 20781251. The next prime is 20781263. The reversal of 20781253 is 35218702.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 20781253 - 2¹ = 20781251 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 (20781251) 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, 335151 + ... + 335212.

It is an arithmetic number, because the mean of its divisors is an integer number (5362912).

Almost surely, 2^20781253 is an apocalyptic number.

It is an amenable number.

20781253 is a deficient number, since it is larger than the sum of its proper divisors (670395).

20781253 is an equidigital number, since it uses as much as digits as its factorization.

20781253 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 670394.

The product of its (nonzero) digits is 3360, while the sum is 28.

The square root of 20781253 is about 4558.6459612477. The cubic root of 20781253 is about 274.9311254513.

Adding to 20781253 its reverse (35218702), we get a palindrome (55999955).

The spelling of 20781253 in words is "twenty million, seven hundred eighty-one thousand, two hundred fifty-three".