18920781 has 12 divisors (see below), whose sum is σ = 29814720. Its totient is φ = 11467080.

The previous prime is 18920773. The next prime is 18920807. The reversal of 18920781 is 18702981.

18920781 = T₁₉₈ + T₁₉₉ + ... + T₄₉₄.

It is not a de Polignac number, because 18920781 - 2³ = 18920773 is a prime.

It is a super-2 number, since 2×18920781² = 715991907299922, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18920701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 95461 + ... + 95658.

It is an arithmetic number, because the mean of its divisors is an integer number (2484560).

Almost surely, 2^18920781 is an apocalyptic number.

18920781 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

18920781 is a deficient number, since it is larger than the sum of its proper divisors (10893939).

18920781 is a wasteful number, since it uses less digits than its factorization.

18920781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 191136 (or 191133 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 36.

The square root of 18920781 is about 4349.8024093055. The cubic root of 18920781 is about 266.4687919225.

It can be divided in two parts, 18920 and 781, that added together give a triangular number (19701 = T₁₉₈).

The spelling of 18920781 in words is "eighteen million, nine hundred twenty thousand, seven hundred eighty-one".