20640212447 has 4 divisors (see below), whose sum is σ = 20659521480. Its totient is φ = 20620903416.

The previous prime is 20640212441. The next prime is 20640212459. The reversal of 20640212447 is 74421204602.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 74421204602 = 2 ⋅37210602301.

It is a cyclic number.

It is not a de Polignac number, because 20640212447 - 2²⁶ = 20573103583 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20640212441) 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, 9652913 + ... + 9655050.

It is an arithmetic number, because the mean of its divisors is an integer number (5164880370).

Almost surely, 2^20640212447 is an apocalyptic number.

20640212447 is a deficient number, since it is larger than the sum of its proper divisors (19309033).

20640212447 is a wasteful number, since it uses less digits than its factorization.

20640212447 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19309032.

The product of its (nonzero) digits is 21504, while the sum is 32.

The spelling of 20640212447 in words is "twenty billion, six hundred forty million, two hundred twelve thousand, four hundred forty-seven".