21123642 has 8 divisors (see below), whose sum is σ = 42247296. Its totient is φ = 7041212.

The previous prime is 21123631. The next prime is 21123643. The reversal of 21123642 is 24632112.

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

21123642 is an admirable number.

It is not an unprimeable number, because it can be changed into a prime (21123643) 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, 1760298 + ... + 1760309.

It is an arithmetic number, because the mean of its divisors is an integer number (5280912).

Almost surely, 2^21123642 is an apocalyptic number.

21123642 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.

21123642 is a wasteful number, since it uses less digits than its factorization.

21123642 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3520612.

The product of its digits is 576, while the sum is 21.

The square root of 21123642 is about 4596.0463444139. The cubic root of 21123642 is about 276.4328170255.

Adding to 21123642 its reverse (24632112), we get a palindrome (45755754).

The spelling of 21123642 in words is "twenty-one million, one hundred twenty-three thousand, six hundred forty-two".