21012538 has 8 divisors (see below), whose sum is σ = 31582260. Its totient is φ = 10485120.

The previous prime is 21012533. The next prime is 21012569. The reversal of 21012538 is 83521012.

It can be written as a sum of positive squares in 2 ways, for example, as 21003889 + 8649 = 4583^2 + 93^2 .

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

It is not an unprimeable number, because it can be changed into a prime (21012533) 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, 9303 + ... + 11338.

Almost surely, 2^21012538 is an apocalyptic number.

21012538 is a deficient number, since it is larger than the sum of its proper divisors (10569722).

21012538 is a wasteful number, since it uses less digits than its factorization.

21012538 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21152.

The product of its (nonzero) digits is 480, while the sum is 22.

The square root of 21012538 is about 4583.9434987792. The cubic root of 21012538 is about 275.9473136847.

The spelling of 21012538 in words is "twenty-one million, twelve thousand, five hundred thirty-eight".