20642407781 has 8 divisors (see below), whose sum is σ = 21202529400. Its totient is φ = 20082403008.

The previous prime is 20642407771. The next prime is 20642407787. The reversal of 20642407781 is 18770424602.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 213422881 + 20428984900 = 14609^2 + 142930^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20642407781 is a prime.

It is a super-2 number, since 2×20642407781² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20642407787) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 422195 + ... + 468543.

It is an arithmetic number, because the mean of its divisors is an integer number (2650316175).

Almost surely, 2^20642407781 is an apocalyptic number.

It is an amenable number.

20642407781 is a deficient number, since it is larger than the sum of its proper divisors (560121619).

20642407781 is a wasteful number, since it uses less digits than its factorization.

20642407781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 58423.

The product of its (nonzero) digits is 150528, while the sum is 41.

The spelling of 20642407781 in words is "twenty billion, six hundred forty-two million, four hundred seven thousand, seven hundred eighty-one".