20400505042 has 4 divisors (see below), whose sum is σ = 30600757566. Its totient is φ = 10200252520.

The previous prime is 20400505033. The next prime is 20400505091. The reversal of 20400505042 is 24050500402.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 24050500402 = 2 ⋅12025250201.

It can be written as a sum of positive squares in only one way, i.e., 18065779281 + 2334725761 = 134409^2 + 48319^2 .

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5100126259 + ... + 5100126262.

Almost surely, 2^20400505042 is an apocalyptic number.

20400505042 is a deficient number, since it is larger than the sum of its proper divisors (10200252524).

20400505042 is a wasteful number, since it uses less digits than its factorization.

20400505042 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10200252523.

The product of its (nonzero) digits is 1600, while the sum is 22.

The spelling of 20400505042 in words is "twenty billion, four hundred million, five hundred five thousand, forty-two".