25550816781 has 32 divisors (see below), whose sum is σ = 39519187200. Its totient is φ = 14382466560.

The previous prime is 25550816779. The next prime is 25550816831. The reversal of 25550816781 is 18761805552.

It is not a de Polignac number, because 25550816781 - 2¹ = 25550816779 is a prime.

It is a super-2 number, since 2×25550816781² (a number of 22 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 25550816781.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (25550816741) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 477351 + ... + 528171.

It is an arithmetic number, because the mean of its divisors is an integer number (1234974600).

Almost surely, 2^25550816781 is an apocalyptic number.

25550816781 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

25550816781 is a deficient number, since it is larger than the sum of its proper divisors (13968370419).

25550816781 is a wasteful number, since it uses less digits than its factorization.

25550816781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51189.

The product of its (nonzero) digits is 672000, while the sum is 48.

The spelling of 25550816781 in words is "twenty-five billion, five hundred fifty million, eight hundred sixteen thousand, seven hundred eighty-one".