21515138 has 8 divisors (see below), whose sum is σ = 32881788. Its totient is φ = 10554544.

The previous prime is 21515113. The next prime is 21515159. The reversal of 21515138 is 83151512.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 19333609 + 2181529 = 4397^2 + 1477^2 .

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

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 101381 + ... + 101592.

Almost surely, 2^21515138 is an apocalyptic number.

21515138 is a deficient number, since it is larger than the sum of its proper divisors (11366650).

21515138 is a wasteful number, since it uses less digits than its factorization.

21515138 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 203028.

The product of its digits is 1200, while the sum is 26.

The square root of 21515138 is about 4638.4413330342. The cubic root of 21515138 is about 278.1301341980.

The spelling of 21515138 in words is "twenty-one million, five hundred fifteen thousand, one hundred thirty-eight".