219649981 has 2 divisors, whose sum is σ = 219649982. Its totient is φ = 219649980.

The previous prime is 219649961. The next prime is 219649987. The reversal of 219649981 is 189946912.

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., 216531225 + 3118756 = 14715^2 + 1766^2 .

It is a cyclic number.

It is not a de Polignac number, because 219649981 - 2⁵ = 219649949 is a prime.

It is a super-2 number, since 2×219649981² = 96492228306600722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (219649987) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 109824990 + 109824991.

It is an arithmetic number, because the mean of its divisors is an integer number (109824991).

Almost surely, 2^219649981 is an apocalyptic number.

It is an amenable number.

219649981 is a deficient number, since it is larger than the sum of its proper divisors (1).

219649981 is an equidigital number, since it uses as much as digits as its factorization.

219649981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 279936, while the sum is 49.

The square root of 219649981 is about 14820.5931392775. The cubic root of 219649981 is about 603.3607524617.

The spelling of 219649981 in words is "two hundred nineteen million, six hundred forty-nine thousand, nine hundred eighty-one".