20729989 has 6 divisors (see below), whose sum is σ = 24114534. Its totient is φ = 17768520.

The previous prime is 20729981. The next prime is 20729993. The reversal of 20729989 is 98992702.

It can be written as a sum of positive squares in only one way, i.e., 17288964 + 3441025 = 4158^2 + 1855^2 .

It is not a de Polignac number, because 20729989 - 2³ = 20729981 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20729981) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 211482 + ... + 211579.

It is an arithmetic number, because the mean of its divisors is an integer number (4019089).

Almost surely, 2^20729989 is an apocalyptic number.

It is an amenable number.

20729989 is a deficient number, since it is larger than the sum of its proper divisors (3384545).

20729989 is an equidigital number, since it uses as much as digits as its factorization.

20729989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 423075 (or 423068 counting only the distinct ones).

The product of its (nonzero) digits is 163296, while the sum is 46.

The square root of 20729989 is about 4553.0197671436. The cubic root of 20729989 is about 274.7048690527.

The spelling of 20729989 in words is "twenty million, seven hundred twenty-nine thousand, nine hundred eighty-nine".