20991373455 has 32 divisors (see below), whose sum is σ = 36218681856. Its totient is φ = 10320234624.

The previous prime is 20991373411. The next prime is 20991373457. The reversal of 20991373455 is 55437319902.

It is a Cunningham number, because it is equal to 144884²-1.

It is not a de Polignac number, because 20991373455 - 2⁹ = 20991372943 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20991373457) by changing a digit.

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 in 31 ways as a sum of consecutive naturals, for example, 72444 + ... + 217326.

It is an arithmetic number, because the mean of its divisors is an integer number (1131833808).

Almost surely, 2^20991373455 is an apocalyptic number.

20991373455 is a deficient number, since it is larger than the sum of its proper divisors (15227308401).

20991373455 is a wasteful number, since it uses less digits than its factorization.

20991373455 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 145647.

The product of its (nonzero) digits is 1020600, while the sum is 48.

The spelling of 20991373455 in words is "twenty billion, nine hundred ninety-one million, three hundred seventy-three thousand, four hundred fifty-five".