20643646 has 4 divisors (see below), whose sum is σ = 30965472. Its totient is φ = 10321822.

The previous prime is 20643643. The next prime is 20643683. The reversal of 20643646 is 64634602.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20643641) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5160910 + ... + 5160913.

It is an arithmetic number, because the mean of its divisors is an integer number (7741368).

Almost surely, 2^20643646 is an apocalyptic number.

20643646 is a deficient number, since it is larger than the sum of its proper divisors (10321826).

20643646 is a wasteful number, since it uses less digits than its factorization.

20643646 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10321825.

The product of its (nonzero) digits is 20736, while the sum is 31.

The square root of 20643646 is about 4543.5279244217. The cubic root of 20643646 is about 274.3229449142.

The spelling of 20643646 in words is "twenty million, six hundred forty-three thousand, six hundred forty-six".