21249957 has 8 divisors (see below), whose sum is σ = 28358784. Its totient is φ = 14153888.

The previous prime is 21249937. The next prime is 21249959. The reversal of 21249957 is 75994212.

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 21249957 - 2⁷ = 21249829 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21249959) 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, 1828 + ... + 6770.

It is an arithmetic number, because the mean of its divisors is an integer number (3544848).

Almost surely, 2^21249957 is an apocalyptic number.

It is an amenable number.

21249957 is a deficient number, since it is larger than the sum of its proper divisors (7108827).

21249957 is a wasteful number, since it uses less digits than its factorization.

21249957 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6379.

The product of its digits is 45360, while the sum is 39.

The square root of 21249957 is about 4609.7675646392. The cubic root of 21249957 is about 276.9827260099.

The spelling of 21249957 in words is "twenty-one million, two hundred forty-nine thousand, nine hundred fifty-seven".