21261242500542 has 128 divisors (see below), whose sum is σ = 51977882787840. Its totient is φ = 6388581888000.

The previous prime is 21261242500471. The next prime is 21261242500577. The reversal of 21261242500542 is 24500524216212.

21261242500542 is a `hidden beast` number, since 2 + 1 + 2 + 61 + 2 + 4 + 2 + 50 + 0 + 542 = 666.

It is a junction number, because it is equal to n+sod(n) for n = 21261242500497 and 21261242500506.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 35211742 + ... + 35810462.

It is an arithmetic number, because the mean of its divisors is an integer number (406077209280).

Almost surely, 2^{21261242500542} is an apocalyptic number.

21261242500542 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 21261242500542, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25988941393920).

21261242500542 is an abundant number, since it is smaller than the sum of its proper divisors (30716640287298).

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

21261242500542 is a wasteful number, since it uses less digits than its factorization.

21261242500542 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 599247 (or 599241 counting only the distinct ones).

The product of its (nonzero) digits is 76800, while the sum is 36.

Adding to 21261242500542 its reverse (24500524216212), we get a palindrome (45761766716754).

The spelling of 21261242500542 in words is "twenty-one trillion, two hundred sixty-one billion, two hundred forty-two million, five hundred thousand, five hundred forty-two".