20639771 has 4 divisors (see below), whose sum is σ = 20930544. Its totient is φ = 20349000.

The previous prime is 20639767. The next prime is 20639779. The reversal of 20639771 is 17793602.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 17793602 = 2 ⋅8896801.

It is a cyclic number.

It is not a de Polignac number, because 20639771 - 2² = 20639767 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20639779) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 145280 + ... + 145421.

It is an arithmetic number, because the mean of its divisors is an integer number (5232636).

Almost surely, 2^20639771 is an apocalyptic number.

20639771 is a deficient number, since it is larger than the sum of its proper divisors (290773).

20639771 is an equidigital number, since it uses as much as digits as its factorization.

20639771 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 290772.

The product of its (nonzero) digits is 15876, while the sum is 35.

The square root of 20639771 is about 4543.1014736631. The cubic root of 20639771 is about 274.3057795367.

The spelling of 20639771 in words is "twenty million, six hundred thirty-nine thousand, seven hundred seventy-one".