20213781 has 8 divisors (see below), whose sum is σ = 30801984. Its totient is φ = 11550720.

The previous prime is 20213761. The next prime is 20213819. The reversal of 20213781 is 18731202.

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

It is not a de Polignac number, because 20213781 - 2⁵ = 20213749 is a prime.

It is a super-2 number, since 2×20213781² = 817193884631922, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20213761) 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, 481260 + ... + 481301.

It is an arithmetic number, because the mean of its divisors is an integer number (3850248).

Almost surely, 2^20213781 is an apocalyptic number.

20213781 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

20213781 is a deficient number, since it is larger than the sum of its proper divisors (10588203).

20213781 is an equidigital number, since it uses as much as digits as its factorization.

20213781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 962571.

The product of its (nonzero) digits is 672, while the sum is 24.

The square root of 20213781 is about 4495.9738655824. The cubic root of 20213781 is about 272.4054875221.

Adding to 20213781 its reverse (18731202), we get a palindrome (38944983).

The spelling of 20213781 in words is "twenty million, two hundred thirteen thousand, seven hundred eighty-one".