21004135 has 4 divisors (see below), whose sum is σ = 25204968. Its totient is φ = 16803304.

The previous prime is 21004117. The next prime is 21004153. The reversal of 21004135 is 53140012.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (21004117) and next prime (21004153).

It is a cyclic number.

It is not a de Polignac number, because 21004135 - 2¹³ = 20995943 is a prime.

It is a Duffinian number.

It is a congruent number.

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, 2100409 + ... + 2100418.

It is an arithmetic number, because the mean of its divisors is an integer number (6301242).

Almost surely, 2^21004135 is an apocalyptic number.

21004135 is a deficient number, since it is larger than the sum of its proper divisors (4200833).

21004135 is an equidigital number, since it uses as much as digits as its factorization.

21004135 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4200832.

The product of its (nonzero) digits is 120, while the sum is 16.

The square root of 21004135 is about 4583.0268382369. The cubic root of 21004135 is about 275.9105246266.

Adding to 21004135 its reverse (53140012), we get a palindrome (74144147).

The spelling of 21004135 in words is "twenty-one million, four thousand, one hundred thirty-five".