21671357 has 2 divisors, whose sum is σ = 21671358. Its totient is φ = 21671356.

The previous prime is 21671347. The next prime is 21671393. The reversal of 21671357 is 75317612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17884441 + 3786916 = 4229^2 + 1946^2 .

It is a cyclic number.

It is not a de Polignac number, because 21671357 - 2⁴ = 21671341 is a prime.

It is equal to p_1369724 and since 21671357 and 1369724 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21671327) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10835678 + 10835679.

It is an arithmetic number, because the mean of its divisors is an integer number (10835679).

Almost surely, 2^21671357 is an apocalyptic number.

It is an amenable number.

21671357 is a deficient number, since it is larger than the sum of its proper divisors (1).

21671357 is an equidigital number, since it uses as much as digits as its factorization.

21671357 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 8820, while the sum is 32.

The square root of 21671357 is about 4655.2504766124. The cubic root of 21671357 is about 278.8016687185.

Adding to 21671357 its reverse (75317612), we get a palindrome (96988969).

The spelling of 21671357 in words is "twenty-one million, six hundred seventy-one thousand, three hundred fifty-seven".