919779221 has 2 divisors, whose sum is σ = 919779222. Its totient is φ = 919779220.

The previous prime is 919779197. The next prime is 919779247. The reversal of 919779221 is 122977919.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 912946225 + 6832996 = 30215^2 + 2614^2 .

It is an emirp because it is prime and its reverse (122977919) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-919779221 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (919779251) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 459889610 + 459889611.

It is an arithmetic number, because the mean of its divisors is an integer number (459889611).

Almost surely, 2^919779221 is an apocalyptic number.

It is an amenable number.

919779221 is a deficient number, since it is larger than the sum of its proper divisors (1).

919779221 is an equidigital number, since it uses as much as digits as its factorization.

919779221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 142884, while the sum is 47.

The square root of 919779221 is about 30327.8621237963. The cubic root of 919779221 is about 972.5110202887.

The spelling of 919779221 in words is "nine hundred nineteen million, seven hundred seventy-nine thousand, two hundred twenty-one".