20385781 has 8 divisors (see below), whose sum is σ = 21995064. Its totient is φ = 18782400.

The previous prime is 20385769. The next prime is 20385791. The reversal of 20385781 is 18758302.

It can be written as a sum of positive squares in 4 ways, for example, as 5716881 + 14668900 = 2391^2 + 3830^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 20385781 - 2⁷ = 20385653 is a prime.

It is a super-2 number, since 2×20385781² = 831160133959922, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20385731) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7995 + ... + 10231.

It is an arithmetic number, because the mean of its divisors is an integer number (2749383).

Almost surely, 2^20385781 is an apocalyptic number.

It is an amenable number.

20385781 is a deficient number, since it is larger than the sum of its proper divisors (1609283).

20385781 is a wasteful number, since it uses less digits than its factorization.

20385781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2951.

The product of its (nonzero) digits is 13440, while the sum is 34.

The square root of 20385781 is about 4515.0615721162. The cubic root of 20385781 is about 273.1759433310.

The spelling of 20385781 in words is "twenty million, three hundred eighty-five thousand, seven hundred eighty-one".