21120402042 has 24 divisors (see below), whose sum is σ = 45763978260. Its totient is φ = 7039656000.

The previous prime is 21120401999. The next prime is 21120402053. The reversal of 21120402042 is 24020402112.

It can be written as a sum of positive squares in 2 ways, for example, as 18463102641 + 2657299401 = 135879^2 + 51549^2 .

It is a Harshad number since it is a multiple of its sum of digits (18).

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 320934 + ... + 381102.

Almost surely, 2^21120402042 is an apocalyptic number.

21120402042 is an abundant number, since it is smaller than the sum of its proper divisors (24643576218).

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

21120402042 is a wasteful number, since it uses less digits than its factorization.

21120402042 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 79678 (or 79675 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 18.

Adding to 21120402042 its reverse (24020402112), we get a palindrome (45140804154).

The spelling of 21120402042 in words is "twenty-one billion, one hundred twenty million, four hundred two thousand, forty-two".