20673781 has 4 divisors (see below), whose sum is σ = 21386700. Its totient is φ = 19960864.

The previous prime is 20673769. The next prime is 20673797. The reversal of 20673781 is 18737602.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 12602500 + 8071281 = 3550^2 + 2841^2 .

It is a cyclic number.

It is not a de Polignac number, because 20673781 - 2¹⁵ = 20641013 is a prime.

It is a super-2 number, since 2×20673781² = 854810441671922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20673701) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 356416 + ... + 356473.

It is an arithmetic number, because the mean of its divisors is an integer number (5346675).

Almost surely, 2^20673781 is an apocalyptic number.

It is an amenable number.

20673781 is a deficient number, since it is larger than the sum of its proper divisors (712919).

20673781 is an equidigital number, since it uses as much as digits as its factorization.

20673781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 712918.

The product of its (nonzero) digits is 14112, while the sum is 34.

The square root of 20673781 is about 4546.8429706776. The cubic root of 20673781 is about 274.4563629273.

The spelling of 20673781 in words is "twenty million, six hundred seventy-three thousand, seven hundred eighty-one".