21661262364540 has 48 divisors (see below), whose sum is σ = 60651950419872. Its totient is φ = 5776297030656.

The previous prime is 21661262364433. The next prime is 21661262364601. The reversal of 21661262364540 is 4546326216612.

It is a self number, because there is not a number n which added to its sum of digits gives 21661262364540.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (29) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8179752 + ... + 10499088.

It is an arithmetic number, because the mean of its divisors is an integer number (1263582300414).

Almost surely, 2^{21661262364540} is an apocalyptic number.

21661262364540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21661262364540 is an abundant number, since it is smaller than the sum of its proper divisors (38990688055332).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21661262364540 is a wasteful number, since it uses less digits than its factorization.

21661262364540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2475006 (or 2475004 counting only the distinct ones).

The product of its (nonzero) digits is 2488320, while the sum is 48.

The spelling of 21661262364540 in words is "twenty-one trillion, six hundred sixty-one billion, two hundred sixty-two million, three hundred sixty-four thousand, five hundred forty".