21257638 has 8 divisors (see below), whose sum is σ = 32986080. Its totient is φ = 10262280.

The previous prime is 21257581. The next prime is 21257651. The reversal of 21257638 is 83675212.

It is a happy number.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 183198 + ... + 183313.

It is an arithmetic number, because the mean of its divisors is an integer number (4123260).

Almost surely, 2^21257638 is an apocalyptic number.

21257638 is a deficient number, since it is larger than the sum of its proper divisors (11728442).

21257638 is a wasteful number, since it uses less digits than its factorization.

21257638 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 366542.

The product of its digits is 20160, while the sum is 34.

The square root of 21257638 is about 4610.6006116340. The cubic root of 21257638 is about 277.0160946740.

The spelling of 21257638 in words is "twenty-one million, two hundred fifty-seven thousand, six hundred thirty-eight".