20471781 has 16 divisors (see below), whose sum is σ = 29998080. Its totient is φ = 12315120.

The previous prime is 20471779. The next prime is 20471809. The reversal of 20471781 is 18717402.

It is not a de Polignac number, because 20471781 - 2¹ = 20471779 is a prime.

It is a super-2 number, since 2×20471781² = 838187634623922, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20471881) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2356 + ... + 6818.

It is an arithmetic number, because the mean of its divisors is an integer number (1874880).

Almost surely, 2^20471781 is an apocalyptic number.

It is an amenable number.

20471781 is a deficient number, since it is larger than the sum of its proper divisors (9526299).

20471781 is a wasteful number, since it uses less digits than its factorization.

20471781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4616.

The product of its (nonzero) digits is 3136, while the sum is 30.

The square root of 20471781 is about 4524.5752286817. The cubic root of 20471781 is about 273.5595468516.

It can be divided in two parts, 2047 and 1781, that added together give a triangular number (3828 = T₈₇).

The spelling of 20471781 in words is "twenty million, four hundred seventy-one thousand, seven hundred eighty-one".