21415253 has 4 divisors (see below), whose sum is σ = 22153740. Its totient is φ = 20676768.

The previous prime is 21415249. The next prime is 21415307. The reversal of 21415253 is 35251412.

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 18037009 + 3378244 = 4247^2 + 1838^2 .

It is not a de Polignac number, because 21415253 - 2² = 21415249 is a prime.

It is a super-2 number, since 2×21415253² = 917226122108018, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21415213) 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, 369200 + ... + 369257.

It is an arithmetic number, because the mean of its divisors is an integer number (5538435).

Almost surely, 2^21415253 is an apocalyptic number.

It is an amenable number.

21415253 is a deficient number, since it is larger than the sum of its proper divisors (738487).

21415253 is an equidigital number, since it uses as much as digits as its factorization.

21415253 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 738486.

The product of its digits is 1200, while the sum is 23.

The square root of 21415253 is about 4627.6617205669. The cubic root of 21415253 is about 277.6990558376.

Adding to 21415253 its reverse (35251412), we get a palindrome (56666665).

The spelling of 21415253 in words is "twenty-one million, four hundred fifteen thousand, two hundred fifty-three".