21253057 has 4 divisors (see below), whose sum is σ = 24289216. Its totient is φ = 18216900.

The previous prime is 21253033. The next prime is 21253093. The reversal of 21253057 is 75035212.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21253057 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21253007) 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, 1518069 + ... + 1518082.

It is an arithmetic number, because the mean of its divisors is an integer number (6072304).

Almost surely, 2^21253057 is an apocalyptic number.

It is an amenable number.

21253057 is a deficient number, since it is larger than the sum of its proper divisors (3036159).

21253057 is an equidigital number, since it uses as much as digits as its factorization.

21253057 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3036158.

The product of its (nonzero) digits is 2100, while the sum is 25.

The square root of 21253057 is about 4610.1037949270. The cubic root of 21253057 is about 276.9961943462.

Adding to 21253057 its reverse (75035212), we get a palindrome (96288269).

The spelling of 21253057 in words is "twenty-one million, two hundred fifty-three thousand, fifty-seven".