20781243 has 18 divisors (see below), whose sum is σ = 34918884. Its totient is φ = 11874744.

The previous prime is 20781239. The next prime is 20781251. The reversal of 20781243 is 34218702.

It is not a de Polignac number, because 20781243 - 2² = 20781239 is a prime.

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (20781223) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 23121 + ... + 24002.

It is an arithmetic number, because the mean of its divisors is an integer number (1939938).

Almost surely, 2^20781243 is an apocalyptic number.

20781243 is a deficient number, since it is larger than the sum of its proper divisors (14137641).

20781243 is a wasteful number, since it uses less digits than its factorization.

20781243 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 47143 (or 47133 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 27.

The square root of 20781243 is about 4558.6448644307. The cubic root of 20781243 is about 274.9310813521.

Adding to 20781243 its reverse (34218702), we get a palindrome (54999945).

It can be divided in two parts, 2078 and 1243, that added together give a triangular number (3321 = T₈₁).

The spelling of 20781243 in words is "twenty million, seven hundred eighty-one thousand, two hundred forty-three".