20781351 has 12 divisors (see below), whose sum is σ = 31322928. Its totient is φ = 13251744.

The previous prime is 20781349. The next prime is 20781367. The reversal of 20781351 is 15318702.

It is not a de Polignac number, because 20781351 - 2¹ = 20781349 is a prime.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20781311) 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 11 ways as a sum of consecutive naturals, for example, 49990 + ... + 50403.

It is an arithmetic number, because the mean of its divisors is an integer number (2610244).

Almost surely, 2^20781351 is an apocalyptic number.

20781351 is a deficient number, since it is larger than the sum of its proper divisors (10541577).

20781351 is a wasteful number, since it uses less digits than its factorization.

20781351 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 100422 (or 100419 counting only the distinct ones).

The product of its (nonzero) digits is 1680, while the sum is 27.

The square root of 20781351 is about 4558.6567100408. The cubic root of 20781351 is about 274.9315576230.

The spelling of 20781351 in words is "twenty million, seven hundred eighty-one thousand, three hundred fifty-one".