215978381 has 2 divisors, whose sum is σ = 215978382. Its totient is φ = 215978380.

The previous prime is 215978363. The next prime is 215978383. The reversal of 215978381 is 183879512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 126202756 + 89775625 = 11234^2 + 9475^2 .

It is a cyclic number.

It is not a de Polignac number, because 215978381 - 2⁶ = 215978317 is a prime.

It is a super-2 number, since 2×215978381² = 93293322118762322, which contains 22 as substring.

Together with 215978383, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (215978383) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 107989190 + 107989191.

It is an arithmetic number, because the mean of its divisors is an integer number (107989191).

Almost surely, 2^215978381 is an apocalyptic number.

It is an amenable number.

215978381 is a deficient number, since it is larger than the sum of its proper divisors (1).

215978381 is an equidigital number, since it uses as much as digits as its factorization.

215978381 is an evil number, because the sum of its binary digits is even.

The product of its digits is 120960, while the sum is 44.

The square root of 215978381 is about 14696.2029449787. The cubic root of 215978381 is about 599.9799817395.

The spelling of 215978381 in words is "two hundred fifteen million, nine hundred seventy-eight thousand, three hundred eighty-one".