21042138 has 32 divisors (see below), whose sum is σ = 45787392. Its totient is φ = 6408000.

The previous prime is 21042127. The next prime is 21042157. The reversal of 21042138 is 83124012.

It is a super-2 number, since 2×21042138² = 885543143222088, which contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6543 + ... + 9213.

It is an arithmetic number, because the mean of its divisors is an integer number (1430856).

Almost surely, 2^21042138 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21042138, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22893696).

21042138 is an abundant number, since it is smaller than the sum of its proper divisors (24745254).

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

21042138 is a wasteful number, since it uses less digits than its factorization.

21042138 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2790.

The product of its (nonzero) digits is 384, while the sum is 21.

The square root of 21042138 is about 4587.1710236267. The cubic root of 21042138 is about 276.0768269638.

The spelling of 21042138 in words is "twenty-one million, forty-two thousand, one hundred thirty-eight".