21315455 has 16 divisors (see below), whose sum is σ = 29374464. Its totient is φ = 14545440.

The previous prime is 21315451. The next prime is 21315491. The reversal of 21315455 is 55451312.

It is not a de Polignac number, because 21315455 - 2² = 21315451 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21315451) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6440 + ... + 9170.

It is an arithmetic number, because the mean of its divisors is an integer number (1835904).

Almost surely, 2^21315455 is an apocalyptic number.

21315455 is a deficient number, since it is larger than the sum of its proper divisors (8059009).

21315455 is a wasteful number, since it uses less digits than its factorization.

21315455 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2966.

The product of its digits is 3000, while the sum is 26.

The square root of 21315455 is about 4616.8663615054. The cubic root of 21315455 is about 277.2670121875.

Adding to 21315455 its reverse (55451312), we get a palindrome (76766767).

The spelling of 21315455 in words is "twenty-one million, three hundred fifteen thousand, four hundred fifty-five".