215551997 has 2 divisors, whose sum is σ = 215551998. Its totient is φ = 215551996.

The previous prime is 215551967. The next prime is 215552003. The reversal of 215551997 is 799155512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 191158276 + 24393721 = 13826^2 + 4939^2 .

It is a cyclic number.

It is not a de Polignac number, because 215551997 - 2⁶ = 215551933 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (215551927) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 107775998 + 107775999.

It is an arithmetic number, because the mean of its divisors is an integer number (107775999).

Almost surely, 2^215551997 is an apocalyptic number.

It is an amenable number.

215551997 is a deficient number, since it is larger than the sum of its proper divisors (1).

215551997 is an equidigital number, since it uses as much as digits as its factorization.

215551997 is an evil number, because the sum of its binary digits is even.

The product of its digits is 141750, while the sum is 44.

The square root of 215551997 is about 14681.6891739336. The cubic root of 215551997 is about 599.5848952871.

The spelling of 215551997 in words is "two hundred fifteen million, five hundred fifty-one thousand, nine hundred ninety-seven".