21257653 has 4 divisors (see below), whose sum is σ = 21272140. Its totient is φ = 21243168.

The previous prime is 21257651. The next prime is 21257669. The reversal of 21257653 is 35675212.

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 11881809 + 9375844 = 3447^2 + 3062^2 .

It is a cyclic number.

It is not a de Polignac number, because 21257653 - 2¹ = 21257651 is a prime.

It is a super-2 number, since 2×21257653² = 903775622136818, which contains 22 as substring.

It is a Duffinian number.

It is a zygodrome in base 3.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21257651) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4758 + ... + 8071.

It is an arithmetic number, because the mean of its divisors is an integer number (5318035).

Almost surely, 2^21257653 is an apocalyptic number.

It is an amenable number.

21257653 is a deficient number, since it is larger than the sum of its proper divisors (14487).

21257653 is a wasteful number, since it uses less digits than its factorization.

21257653 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14486.

The product of its digits is 12600, while the sum is 31.

The square root of 21257653 is about 4610.6022383198. The cubic root of 21257653 is about 277.0161598309.

The spelling of 21257653 in words is "twenty-one million, two hundred fifty-seven thousand, six hundred fifty-three".