21303657 has 6 divisors (see below), whose sum is σ = 30771962. Its totient is φ = 14202432.

The previous prime is 21303649. The next prime is 21303671. The reversal of 21303657 is 75630312.

It is a happy number.

21303657 is a `hidden beast` number, since 2 + 1 + 3 + 0 + 3 + 657 = 666.

It can be written as a sum of positive squares in only one way, i.e., 20985561 + 318096 = 4581^2 + 564^2 .

It is not a de Polignac number, because 21303657 - 2³ = 21303649 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21303657.

It is not an unprimeable number, because it can be changed into a prime (21303697) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1183528 + ... + 1183545.

Almost surely, 2^21303657 is an apocalyptic number.

It is an amenable number.

21303657 is a deficient number, since it is larger than the sum of its proper divisors (9468305).

21303657 is a wasteful number, since it uses less digits than its factorization.

21303657 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2367079 (or 2367076 counting only the distinct ones).

The product of its (nonzero) digits is 3780, while the sum is 27.

The square root of 21303657 is about 4615.5884781900. The cubic root of 21303657 is about 277.2158474352.

Adding to 21303657 its reverse (75630312), we get a palindrome (96933969).

The spelling of 21303657 in words is "twenty-one million, three hundred three thousand, six hundred fifty-seven".