21120042042 has 72 divisors (see below), whose sum is σ = 50360188788. Its totient is φ = 6392136960.

The previous prime is 21120042023. The next prime is 21120042061. The reversal of 21120042042 is 24024002112.

21120042042 is a `hidden beast` number, since 2 + 1 + 1 + 200 + 420 + 42 = 666.

It is an interprime number because it is at equal distance from previous prime (21120042023) and next prime (21120042061).

It can be written as a sum of positive squares in 2 ways, for example, as 21111799401 + 8242641 = 145299^2 + 2871^2 .

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

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 1904578 + ... + 1915634.

Almost surely, 2^21120042042 is an apocalyptic number.

21120042042 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 21120042042, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25180094394).

21120042042 is an abundant number, since it is smaller than the sum of its proper divisors (29240146746).

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

21120042042 is a wasteful number, since it uses less digits than its factorization.

21120042042 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11964 (or 11950 counting only the distinct ones).

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

Adding to 21120042042 its reverse (24024002112), we get a palindrome (45144044154).

The spelling of 21120042042 in words is "twenty-one billion, one hundred twenty million, forty-two thousand, forty-two".