20405781925 has 6 divisors (see below), whose sum is σ = 25303169618. Its totient is φ = 16324625520.

The previous prime is 20405781911. The next prime is 20405781973. The reversal of 20405781925 is 52918750402.

It can be written as a sum of positive squares in 3 ways, for example, as 2600082081 + 17805699844 = 50991^2 + 133438^2 .

It is not a de Polignac number, because 20405781925 - 2¹³ = 20405773733 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 408115614 + ... + 408115663.

Almost surely, 2^20405781925 is an apocalyptic number.

20405781925 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

20405781925 is a deficient number, since it is larger than the sum of its proper divisors (4897387693).

20405781925 is an equidigital number, since it uses as much as digits as its factorization.

20405781925 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 816231287 (or 816231282 counting only the distinct ones).

The product of its (nonzero) digits is 201600, while the sum is 43.

The spelling of 20405781925 in words is "twenty billion, four hundred five million, seven hundred eighty-one thousand, nine hundred twenty-five".