21251138 has 8 divisors (see below), whose sum is σ = 31961088. Its totient is φ = 10597444.

The previous prime is 21251137. The next prime is 21251141. The reversal of 21251138 is 83115212.

It is a happy number.

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

It is a super-2 number, since 2×21251138² = 903221732590088, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21251137) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13106 + ... + 14637.

It is an arithmetic number, because the mean of its divisors is an integer number (3995136).

Almost surely, 2^21251138 is an apocalyptic number.

21251138 is a deficient number, since it is larger than the sum of its proper divisors (10709950).

21251138 is a wasteful number, since it uses less digits than its factorization.

21251138 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28128.

The product of its digits is 480, while the sum is 23.

The square root of 21251138 is about 4609.8956604244. The cubic root of 21251138 is about 276.9878571660.

The spelling of 21251138 in words is "twenty-one million, two hundred fifty-one thousand, one hundred thirty-eight".