21012205542 has 64 divisors (see below), whose sum is σ = 45457735680. Its totient is φ = 6455988000.

The previous prime is 21012205493. The next prime is 21012205553. The reversal of 21012205542 is 24550221012.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1012167 + ... + 1032717.

It is an arithmetic number, because the mean of its divisors is an integer number (710277120).

Almost surely, 2^21012205542 is an apocalyptic number.

21012205542 is an abundant number, since it is smaller than the sum of its proper divisors (24445530138).

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

21012205542 is a wasteful number, since it uses less digits than its factorization.

21012205542 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20849.

The product of its (nonzero) digits is 1600, while the sum is 24.

Adding to 21012205542 its reverse (24550221012), we get a palindrome (45562426554).

The spelling of 21012205542 in words is "twenty-one billion, twelve million, two hundred five thousand, five hundred forty-two".