215665531 has 2 divisors, whose sum is σ = 215665532. Its totient is φ = 215665530.

The previous prime is 215665529. The next prime is 215665573. The reversal of 215665531 is 135566512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 215665531 - 2¹ = 215665529 is a prime.

It is a super-2 number, since 2×215665531² = 93023242523023922, which contains 22 as substring.

Together with 215665529, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (215665501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 107832765 + 107832766.

It is an arithmetic number, because the mean of its divisors is an integer number (107832766).

Almost surely, 2^215665531 is an apocalyptic number.

215665531 is a deficient number, since it is larger than the sum of its proper divisors (1).

215665531 is an equidigital number, since it uses as much as digits as its factorization.

215665531 is an evil number, because the sum of its binary digits is even.

The product of its digits is 27000, while the sum is 34.

The square root of 215665531 is about 14685.5551818786. Note that the first 3 decimals coincide. The cubic root of 215665531 is about 599.6901464937.

The spelling of 215665531 in words is "two hundred fifteen million, six hundred sixty-five thousand, five hundred thirty-one".