21275538 has 16 divisors (see below), whose sum is σ = 42744576. Its totient is φ = 7059600.

The previous prime is 21275533. The next prime is 21275543. The reversal of 21275538 is 83557212.

It is an interprime number because it is at equal distance from previous prime (21275533) and next prime (21275543).

It is a junction number, because it is equal to n+sod(n) for n = 21275499 and 21275508.

It is not an unprimeable number, because it can be changed into a prime (21275533) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6613 + ... + 9288.

It is an arithmetic number, because the mean of its divisors is an integer number (2671536).

Almost surely, 2^21275538 is an apocalyptic number.

21275538 is an abundant number, since it is smaller than the sum of its proper divisors (21469038).

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

21275538 is a wasteful number, since it uses less digits than its factorization.

21275538 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16129.

The product of its digits is 16800, while the sum is 33.

The square root of 21275538 is about 4612.5413819282. The cubic root of 21275538 is about 277.0938266866.

The spelling of 21275538 in words is "twenty-one million, two hundred seventy-five thousand, five hundred thirty-eight".