21384457 has 8 divisors (see below), whose sum is σ = 22648896. Its totient is φ = 20147952.

The previous prime is 21384449. The next prime is 21384479. The reversal of 21384457 is 75448312.

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 21384457 - 2³ = 21384449 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21384257) 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, 5398 + ... + 8479.

It is an arithmetic number, because the mean of its divisors is an integer number (2831112).

Almost surely, 2^21384457 is an apocalyptic number.

It is an amenable number.

21384457 is a deficient number, since it is larger than the sum of its proper divisors (1264439).

21384457 is a wasteful number, since it uses less digits than its factorization.

21384457 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13967.

The product of its digits is 26880, while the sum is 34.

The square root of 21384457 is about 4624.3331411134. Note that the first 3 decimals coincide. The cubic root of 21384457 is about 277.5658778206.

The spelling of 21384457 in words is "twenty-one million, three hundred eighty-four thousand, four hundred fifty-seven".