20640356 has 12 divisors (see below), whose sum is σ = 39404400. Its totient is φ = 9381960.

The previous prime is 20640331. The next prime is 20640391. The reversal of 20640356 is 65304602.

It is an unprimeable number.

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, 234506 + ... + 234593.

It is an arithmetic number, because the mean of its divisors is an integer number (3283700).

Almost surely, 2^20640356 is an apocalyptic number.

It is an amenable number.

20640356 is a deficient number, since it is larger than the sum of its proper divisors (18764044).

20640356 is a wasteful number, since it uses less digits than its factorization.

20640356 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 469114 (or 469112 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 26.

The square root of 20640356 is about 4543.1658565366. The cubic root of 20640356 is about 274.3083710926.

Adding to 20640356 its reverse (65304602), we get a palindrome (85944958).

The spelling of 20640356 in words is "twenty million, six hundred forty thousand, three hundred fifty-six".