21958361 has 2 divisors, whose sum is σ = 21958362. Its totient is φ = 21958360.

The previous prime is 21958303. The next prime is 21958367. The reversal of 21958361 is 16385912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16810000 + 5148361 = 4100^2 + 2269^2 .

It is a cyclic number.

It is not a de Polignac number, because 21958361 - 2¹⁰ = 21957337 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is equal to p_1386818 and since 21958361 and 1386818 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (21958367) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10979180 + 10979181.

It is an arithmetic number, because the mean of its divisors is an integer number (10979181).

Almost surely, 2^21958361 is an apocalyptic number.

It is an amenable number.

21958361 is a deficient number, since it is larger than the sum of its proper divisors (1).

21958361 is an equidigital number, since it uses as much as digits as its factorization.

21958361 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12960, while the sum is 35.

The square root of 21958361 is about 4685.9749252423. The cubic root of 21958361 is about 280.0270424562.

The spelling of 21958361 in words is "twenty-one million, nine hundred fifty-eight thousand, three hundred sixty-one".