21018939 has 8 divisors (see below), whose sum is σ = 28991760. Its totient is φ = 13529376.

The previous prime is 21018931. The next prime is 21018947. The reversal of 21018939 is 93981012.

It is an interprime number because it is at equal distance from previous prime (21018931) and next prime (21018947).

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

It is not a de Polignac number, because 21018939 - 2³ = 21018931 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21018931) 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, 120712 + ... + 120885.

It is an arithmetic number, because the mean of its divisors is an integer number (3623970).

Almost surely, 2^21018939 is an apocalyptic number.

21018939 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

21018939 is a deficient number, since it is larger than the sum of its proper divisors (7972821).

21018939 is a wasteful number, since it uses less digits than its factorization.

21018939 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 241629.

The product of its (nonzero) digits is 3888, while the sum is 33.

The square root of 21018939 is about 4584.6416435748. The cubic root of 21018939 is about 275.9753312335.

The spelling of 21018939 in words is "twenty-one million, eighteen thousand, nine hundred thirty-nine".