19770991 has 2 divisors, whose sum is σ = 19770992. Its totient is φ = 19770990.

The previous prime is 19770977. The next prime is 19771009. The reversal of 19770991 is 19907791.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 19770991 - 2⁹ = 19770479 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19770941) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9885495 + 9885496.

It is an arithmetic number, because the mean of its divisors is an integer number (9885496).

Almost surely, 2^19770991 is an apocalyptic number.

19770991 is a deficient number, since it is larger than the sum of its proper divisors (1).

19770991 is an equidigital number, since it uses as much as digits as its factorization.

19770991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 35721, while the sum is 43.

The square root of 19770991 is about 4446.4582534867. The cubic root of 19770991 is about 270.4017384827.

The spelling of 19770991 in words is "nineteen million, seven hundred seventy thousand, nine hundred ninety-one".