21249021 has 8 divisors (see below), whose sum is σ = 28475200. Its totient is φ = 14094432.

The previous prime is 21248977. The next prime is 21249047. The reversal of 21249021 is 12094212.

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

It is not a de Polignac number, because 21249021 - 2⁶ = 21248957 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 (21209021) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 17200 + ... + 18393.

It is an arithmetic number, because the mean of its divisors is an integer number (3559400).

Almost surely, 2^21249021 is an apocalyptic number.

It is an amenable number.

21249021 is a deficient number, since it is larger than the sum of its proper divisors (7226179).

21249021 is a wasteful number, since it uses less digits than its factorization.

21249021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 35795.

The product of its (nonzero) digits is 288, while the sum is 21.

The square root of 21249021 is about 4609.6660399643. Note that the first 3 decimals coincide. The cubic root of 21249021 is about 276.9786591838.

The spelling of 21249021 in words is "twenty-one million, two hundred forty-nine thousand, twenty-one".