21571357 has 2 divisors, whose sum is σ = 21571358. Its totient is φ = 21571356.

The previous prime is 21571343. The next prime is 21571367. The reversal of 21571357 is 75317512.

21571357 is nontrivially palindromic in base 7.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21335161 + 236196 = 4619^2 + 486^2 .

It is a cyclic number.

It is not a de Polignac number, because 21571357 - 2⁷ = 21571229 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21571367) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10785678 + 10785679.

It is an arithmetic number, because the mean of its divisors is an integer number (10785679).

Almost surely, 2^21571357 is an apocalyptic number.

It is an amenable number.

21571357 is a deficient number, since it is larger than the sum of its proper divisors (1).

21571357 is an equidigital number, since it uses as much as digits as its factorization.

21571357 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7350, while the sum is 31.

The square root of 21571357 is about 4644.4974970388. The cubic root of 21571357 is about 278.3721746106.

Adding to 21571357 its reverse (75317512), we get a palindrome (96888869).

The spelling of 21571357 in words is "twenty-one million, five hundred seventy-one thousand, three hundred fifty-seven".