20408781 has 8 divisors (see below), whose sum is σ = 27556480. Its totient is φ = 13433472.

The previous prime is 20408747. The next prime is 20408783. The reversal of 20408781 is 18780402.

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

It is not a de Polignac number, because 20408781 - 2¹⁴ = 20392397 is a prime.

It is a super-2 number, since 2×20408781² = 833036683811922, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20408783) 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, 42820 + ... + 43293.

It is an arithmetic number, because the mean of its divisors is an integer number (3444560).

Almost surely, 2^20408781 is an apocalyptic number.

It is an amenable number.

20408781 is a deficient number, since it is larger than the sum of its proper divisors (7147699).

20408781 is an equidigital number, since it uses as much as digits as its factorization.

20408781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 86195.

The product of its (nonzero) digits is 3584, while the sum is 30.

The square root of 20408781 is about 4517.6078847107. The cubic root of 20408781 is about 273.2786404879.

The spelling of 20408781 in words is "twenty million, four hundred eight thousand, seven hundred eighty-one".