21253249 has 4 divisors (see below), whose sum is σ = 21272836. Its totient is φ = 21233664.

The previous prime is 21253241. The next prime is 21253277. The reversal of 21253249 is 94235212.

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

It can be written as a sum of positive squares in 2 ways, for example, as 14493249 + 6760000 = 3807^2 + 2600^2 .

It is a 3-Lehmer number, since φ(21253249) divides (21253249-1)³.

It is a cyclic number.

It is not a de Polignac number, because 21253249 - 2³ = 21253241 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21253241) 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, 8064 + ... + 10369.

It is an arithmetic number, because the mean of its divisors is an integer number (5318209).

Almost surely, 2^21253249 is an apocalyptic number.

It is an amenable number.

21253249 is a deficient number, since it is larger than the sum of its proper divisors (19587).

21253249 is a wasteful number, since it uses less digits than its factorization.

21253249 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19586.

The product of its digits is 4320, while the sum is 28.

The square root of 21253249 is about 4610.1246187061. The cubic root of 21253249 is about 276.9970284710.

The spelling of 21253249 in words is "twenty-one million, two hundred fifty-three thousand, two hundred forty-nine".