21254815 has 4 divisors (see below), whose sum is σ = 25505784. Its totient is φ = 17003848.

The previous prime is 21254813. The next prime is 21254819. The reversal of 21254815 is 51845212.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21254815 - 2¹ = 21254813 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21254813) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2125477 + ... + 2125486.

It is an arithmetic number, because the mean of its divisors is an integer number (6376446).

Almost surely, 2^21254815 is an apocalyptic number.

21254815 is a deficient number, since it is larger than the sum of its proper divisors (4250969).

21254815 is an equidigital number, since it uses as much as digits as its factorization.

21254815 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4250968.

The product of its digits is 3200, while the sum is 28.

The square root of 21254815 is about 4610.2944591425. The cubic root of 21254815 is about 277.0038316143.

The spelling of 21254815 in words is "twenty-one million, two hundred fifty-four thousand, eight hundred fifteen".