21509051 has 8 divisors (see below), whose sum is σ = 22153824. Its totient is φ = 20870080.

The previous prime is 21509041. The next prime is 21509057. The reversal of 21509051 is 15090512.

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

It is a cyclic number.

It is not a de Polignac number, because 21509051 - 2¹⁰ = 21508027 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21509057) 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 7 ways as a sum of consecutive naturals, for example, 6746 + ... + 9408.

It is an arithmetic number, because the mean of its divisors is an integer number (2769228).

Almost surely, 2^21509051 is an apocalyptic number.

21509051 is a deficient number, since it is larger than the sum of its proper divisors (644773).

21509051 is a wasteful number, since it uses less digits than its factorization.

21509051 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2901.

The product of its (nonzero) digits is 450, while the sum is 23.

The square root of 21509051 is about 4637.7851394820. The cubic root of 21509051 is about 278.1039024690.

Adding to 21509051 its reverse (15090512), we get a palindrome (36599563).

The spelling of 21509051 in words is "twenty-one million, five hundred nine thousand, fifty-one".