21870042 has 8 divisors (see below), whose sum is σ = 43740096. Its totient is φ = 7290012.

The previous prime is 21870029. The next prime is 21870047. The reversal of 21870042 is 24007812.

It is a sphenic number, since it is the product of 3 distinct primes.

21870042 is an admirable number.

It is a junction number, because it is equal to n+sod(n) for n = 21869994 and 21870021.

It is not an unprimeable number, because it can be changed into a prime (21870047) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1822498 + ... + 1822509.

It is an arithmetic number, because the mean of its divisors is an integer number (5467512).

Almost surely, 2^21870042 is an apocalyptic number.

21870042 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21870042 is a wasteful number, since it uses less digits than its factorization.

21870042 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3645012.

The product of its (nonzero) digits is 896, while the sum is 24.

The square root of 21870042 is about 4676.5416709359. The cubic root of 21870042 is about 279.6511045532.

Adding to 21870042 its reverse (24007812), we get a palindrome (45877854).

The spelling of 21870042 in words is "twenty-one million, eight hundred seventy thousand, forty-two".