21021240042 has 40 divisors (see below), whose sum is σ = 51385257792. Its totient is φ = 6370072200.

The previous prime is 21021240041. The next prime is 21021240059. The reversal of 21021240042 is 24004212012.

21021240042 is a `hidden beast` number, since 2 + 10 + 212 + 400 + 42 = 666.

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

It is a junction number, because it is equal to n+sod(n) for n = 21021239997 and 21021240024.

It is not an unprimeable number, because it can be changed into a prime (21021240041) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 5896434 + ... + 5899997.

Almost surely, 2^21021240042 is an apocalyptic number.

21021240042 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

21021240042 is an abundant number, since it is smaller than the sum of its proper divisors (30364017750).

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

21021240042 is a wasteful number, since it uses less digits than its factorization.

21021240042 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11796456 (or 11796447 counting only the distinct ones).

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

Adding to 21021240042 its reverse (24004212012), we get a palindrome (45025452054).

The spelling of 21021240042 in words is "twenty-one billion, twenty-one million, two hundred forty thousand, forty-two".