21090047 has 16 divisors (see below), whose sum is σ = 25207200. Its totient is φ = 17418240.

The previous prime is 21090007. The next prime is 21090061. The reversal of 21090047 is 74009012.

It is a cyclic number.

It is not a de Polignac number, because 21090047 - 2⁶ = 21089983 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21090007) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3479 + ... + 7367.

It is an arithmetic number, because the mean of its divisors is an integer number (1575450).

Almost surely, 2^21090047 is an apocalyptic number.

21090047 is a deficient number, since it is larger than the sum of its proper divisors (4117153).

21090047 is a wasteful number, since it uses less digits than its factorization.

21090047 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3946.

The product of its (nonzero) digits is 504, while the sum is 23.

The square root of 21090047 is about 4592.3901184459. The cubic root of 21090047 is about 276.2861931927.

Adding to 21090047 its reverse (74009012), we get a palindrome (95099059).

The spelling of 21090047 in words is "twenty-one million, ninety thousand, forty-seven".