21012253 has 4 divisors (see below), whose sum is σ = 21033628. Its totient is φ = 20990880.

The previous prime is 21012241. The next prime is 21012259. The reversal of 21012253 is 35221012.

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 17489124 + 3523129 = 4182^2 + 1877^2 .

It is a cyclic number.

It is not a de Polignac number, because 21012253 - 2⁹ = 21011741 is a prime.

It is a super-2 number, since 2×21012253² = 883029552272018, 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 (21012259) 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, 9138 + ... + 11203.

It is an arithmetic number, because the mean of its divisors is an integer number (5258407).

Almost surely, 2^21012253 is an apocalyptic number.

It is an amenable number.

21012253 is a deficient number, since it is larger than the sum of its proper divisors (21375).

21012253 is a wasteful number, since it uses less digits than its factorization.

21012253 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21374.

The product of its (nonzero) digits is 120, while the sum is 16.

The square root of 21012253 is about 4583.9124119032. The cubic root of 21012253 is about 275.9460660909.

Adding to 21012253 its reverse (35221012), we get a palindrome (56233265).

The spelling of 21012253 in words is "twenty-one million, twelve thousand, two hundred fifty-three".