21018538 has 8 divisors (see below), whose sum is σ = 31704480. Its totient is φ = 10450380.

The previous prime is 21018523. The next prime is 21018539. The reversal of 21018538 is 83581012.

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 (21018539) 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, 28998 + ... + 29713.

It is an arithmetic number, because the mean of its divisors is an integer number (3963060).

Almost surely, 2^21018538 is an apocalyptic number.

21018538 is a deficient number, since it is larger than the sum of its proper divisors (10685942).

21018538 is a wasteful number, since it uses less digits than its factorization.

21018538 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 58892.

The product of its (nonzero) digits is 1920, while the sum is 28.

The square root of 21018538 is about 4584.5979103952. The cubic root of 21018538 is about 275.9735762003.

The spelling of 21018538 in words is "twenty-one million, eighteen thousand, five hundred thirty-eight".