215213981 has 2 divisors, whose sum is σ = 215213982. Its totient is φ = 215213980.

The previous prime is 215213963. The next prime is 215213989. The reversal of 215213981 is 189312512.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 147233956 + 67980025 = 12134^2 + 8245^2 .

It is a cyclic number.

It is not a de Polignac number, because 215213981 - 2¹⁸ = 214951837 is a prime.

It is a super-2 number, since 2×215213981² = 92634115235736722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (215213989) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 107606990 + 107606991.

It is an arithmetic number, because the mean of its divisors is an integer number (107606991).

Almost surely, 2^215213981 is an apocalyptic number.

It is an amenable number.

215213981 is a deficient number, since it is larger than the sum of its proper divisors (1).

215213981 is an equidigital number, since it uses as much as digits as its factorization.

215213981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4320, while the sum is 32.

The square root of 215213981 is about 14670.1731755286. The cubic root of 215213981 is about 599.2713200304.

The spelling of 215213981 in words is "two hundred fifteen million, two hundred thirteen thousand, nine hundred eighty-one".