20749409 has 4 divisors (see below), whose sum is σ = 20830404. Its totient is φ = 20668416.

The previous prime is 20749369. The next prime is 20749423. The reversal of 20749409 is 90494702.

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 20566225 + 183184 = 4535^2 + 428^2 .

It is a cyclic number.

It is not a de Polignac number, because 20749409 - 2²⁰ = 19700833 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20749909) 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, 40112 + ... + 40625.

It is an arithmetic number, because the mean of its divisors is an integer number (5207601).

Almost surely, 2^20749409 is an apocalyptic number.

It is an amenable number.

20749409 is a deficient number, since it is larger than the sum of its proper divisors (80995).

20749409 is an equidigital number, since it uses as much as digits as its factorization.

20749409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80994.

The product of its (nonzero) digits is 18144, while the sum is 35.

The square root of 20749409 is about 4555.1519184326. The cubic root of 20749409 is about 274.7906240996.

The spelling of 20749409 in words is "twenty million, seven hundred forty-nine thousand, four hundred nine".