21004131 has 4 divisors (see below), whose sum is σ = 28005512. Its totient is φ = 14002752.

The previous prime is 21004117. The next prime is 21004153. The reversal of 21004131 is 13140012.

It is a happy number.

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

It is not a de Polignac number, because 21004131 - 2⁵ = 21004099 is a prime.

It is a super-2 number, since 2×21004131² = 882347038130322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21004331) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3500686 + ... + 3500691.

It is an arithmetic number, because the mean of its divisors is an integer number (7001378).

Almost surely, 2^21004131 is an apocalyptic number.

21004131 is a deficient number, since it is larger than the sum of its proper divisors (7001381).

21004131 is an equidigital number, since it uses as much as digits as its factorization.

21004131 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7001380.

The product of its (nonzero) digits is 24, while the sum is 12.

The square root of 21004131 is about 4583.0264018441. The cubic root of 21004131 is about 275.9105071120.

Adding to 21004131 its reverse (13140012), we get a palindrome (34144143).

The spelling of 21004131 in words is "twenty-one million, four thousand, one hundred thirty-one".