215520251 has 2 divisors, whose sum is σ = 215520252. Its totient is φ = 215520250.

The previous prime is 215520209. The next prime is 215520269. The reversal of 215520251 is 152025512.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-215520251 is a prime.

It is a super-2 number, since 2×215520251² = 92897957182206002, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (215520551) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 107760125 + 107760126.

It is an arithmetic number, because the mean of its divisors is an integer number (107760126).

Almost surely, 2^215520251 is an apocalyptic number.

215520251 is a deficient number, since it is larger than the sum of its proper divisors (1).

215520251 is an equidigital number, since it uses as much as digits as its factorization.

215520251 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1000, while the sum is 23.

The square root of 215520251 is about 14680.6079914968. The cubic root of 215520251 is about 599.5554586827. Note that the first 3 decimals are identical.

Adding to 215520251 its reverse (152025512), we get a palindrome (367545763).

The spelling of 215520251 in words is "two hundred fifteen million, five hundred twenty thousand, two hundred fifty-one".