20487781 has 4 divisors (see below), whose sum is σ = 20747200. Its totient is φ = 20228364.

The previous prime is 20487773. The next prime is 20487787. The reversal of 20487781 is 18778402.

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 20487781 - 2³ = 20487773 is a prime.

It is a super-2 number, since 2×20487781² = 839498340607922, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20487781.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20487787) 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 3 ways as a sum of consecutive naturals, for example, 129591 + ... + 129748.

It is an arithmetic number, because the mean of its divisors is an integer number (5186800).

Almost surely, 2^20487781 is an apocalyptic number.

It is an amenable number.

20487781 is a deficient number, since it is larger than the sum of its proper divisors (259419).

20487781 is an equidigital number, since it uses as much as digits as its factorization.

20487781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 259418.

The product of its (nonzero) digits is 25088, while the sum is 37.

The square root of 20487781 is about 4526.3430051201. The cubic root of 20487781 is about 273.6307963593.

The spelling of 20487781 in words is "twenty million, four hundred eighty-seven thousand, seven hundred eighty-one".