21387455 has 8 divisors (see below), whose sum is σ = 25778400. Its totient is φ = 17034336.

The previous prime is 21387451. The next prime is 21387463. The reversal of 21387455 is 55478312.

It is a happy number.

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 21387455 - 2² = 21387451 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21387451) 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, 8195 + ... + 10484.

It is an arithmetic number, because the mean of its divisors is an integer number (3222300).

Almost surely, 2^21387455 is an apocalyptic number.

21387455 is a deficient number, since it is larger than the sum of its proper divisors (4390945).

21387455 is a wasteful number, since it uses less digits than its factorization.

21387455 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18913.

The product of its digits is 33600, while the sum is 35.

The square root of 21387455 is about 4624.6572845996. The cubic root of 21387455 is about 277.5788483567.

The spelling of 21387455 in words is "twenty-one million, three hundred eighty-seven thousand, four hundred fifty-five".