20640587 has 4 divisors (see below), whose sum is σ = 22517016. Its totient is φ = 18764160.

The previous prime is 20640583. The next prime is 20640617. The reversal of 20640587 is 78504602.

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

It is a cyclic number.

It is not a de Polignac number, because 20640587 - 2² = 20640583 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20640583) 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, 938198 + ... + 938219.

It is an arithmetic number, because the mean of its divisors is an integer number (5629254).

Almost surely, 2^20640587 is an apocalyptic number.

20640587 is a deficient number, since it is larger than the sum of its proper divisors (1876429).

20640587 is a wasteful number, since it uses less digits than its factorization.

20640587 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1876428.

The product of its (nonzero) digits is 13440, while the sum is 32.

The square root of 20640587 is about 4543.1912792662. The cubic root of 20640587 is about 274.3093944115.

The spelling of 20640587 in words is "twenty million, six hundred forty thousand, five hundred eighty-seven".