21168657 has 6 divisors (see below), whose sum is σ = 30576962. Its totient is φ = 14112432.

The previous prime is 21168649. The next prime is 21168701. The reversal of 21168657 is 75686112.

It can be written as a sum of positive squares in only one way, i.e., 12383361 + 8785296 = 3519^2 + 2964^2 .

It is not a de Polignac number, because 21168657 - 2³ = 21168649 is a prime.

It is a super-2 number, since 2×21168657² = 896224078367298, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21169657) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1176028 + ... + 1176045.

Almost surely, 2^21168657 is an apocalyptic number.

It is an amenable number.

21168657 is a deficient number, since it is larger than the sum of its proper divisors (9408305).

21168657 is a wasteful number, since it uses less digits than its factorization.

21168657 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2352079 (or 2352076 counting only the distinct ones).

The product of its digits is 20160, while the sum is 36.

The square root of 21168657 is about 4600.9408820371. The cubic root of 21168657 is about 276.6290394144.

The spelling of 21168657 in words is "twenty-one million, one hundred sixty-eight thousand, six hundred fifty-seven".