21090049 has 4 divisors (see below), whose sum is σ = 21102336. Its totient is φ = 21077764.

The previous prime is 21090007. The next prime is 21090061. The reversal of 21090049 is 94009012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21090049 - 2⁷ = 21089921 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21010049) 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, 3049 + ... + 7174.

It is an arithmetic number, because the mean of its divisors is an integer number (5275584).

Almost surely, 2^21090049 is an apocalyptic number.

It is an amenable number.

21090049 is a deficient number, since it is larger than the sum of its proper divisors (12287).

21090049 is a wasteful number, since it uses less digits than its factorization.

21090049 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12286.

The product of its (nonzero) digits is 648, while the sum is 25.

The square root of 21090049 is about 4592.3903361975. The cubic root of 21090049 is about 276.2862019262.

The spelling of 21090049 in words is "twenty-one million, ninety thousand, forty-nine".