20501609 has 4 divisors (see below), whose sum is σ = 21707604. Its totient is φ = 19295616.

The previous prime is 20501587. The next prime is 20501623. The reversal of 20501609 is 90610502.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 90610502 = 2 ⋅45305251.

It can be written as a sum of positive squares in 2 ways, for example, as 18619225 + 1882384 = 4315^2 + 1372^2 .

It is a cyclic number.

It is not a de Polignac number, because 20501609 - 2²⁴ = 3724393 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20501699) 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, 602972 + ... + 603005.

It is an arithmetic number, because the mean of its divisors is an integer number (5426901).

Almost surely, 2^20501609 is an apocalyptic number.

It is an amenable number.

20501609 is a deficient number, since it is larger than the sum of its proper divisors (1205995).

20501609 is a wasteful number, since it uses less digits than its factorization.

20501609 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1205994.

The product of its (nonzero) digits is 540, while the sum is 23.

The square root of 20501609 is about 4527.8702499078. The cubic root of 20501609 is about 273.6923438690.

The spelling of 20501609 in words is "twenty million, five hundred one thousand, six hundred nine".