21220357 has 2 divisors, whose sum is σ = 21220358. Its totient is φ = 21220356.

The previous prime is 21220349. The next prime is 21220379. The reversal of 21220357 is 75302212.

It is an a-pointer prime, because the next prime (21220379) can be obtained adding 21220357 to its sum of digits (22).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19660356 + 1560001 = 4434^2 + 1249^2 .

It is a cyclic number.

It is not a de Polignac number, because 21220357 - 2³ = 21220349 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21220327) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10610178 + 10610179.

It is an arithmetic number, because the mean of its divisors is an integer number (10610179).

Almost surely, 2^21220357 is an apocalyptic number.

It is an amenable number.

21220357 is a deficient number, since it is larger than the sum of its proper divisors (1).

21220357 is an equidigital number, since it uses as much as digits as its factorization.

21220357 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 840, while the sum is 22.

The square root of 21220357 is about 4606.5558717984. Note that the first 3 decimals coincide. The cubic root of 21220357 is about 276.8540591078.

Adding to 21220357 its reverse (75302212), we get a palindrome (96522569).

The spelling of 21220357 in words is "twenty-one million, two hundred twenty thousand, three hundred fifty-seven".