19995551 has 2 divisors, whose sum is σ = 19995552. Its totient is φ = 19995550.

The previous prime is 19995523. The next prime is 19995583. The reversal of 19995551 is 15559991.

It is a happy number.

It is a weak prime.

It is an emirp because it is prime and its reverse (15559991) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-19995551 is a prime.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19995851) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9997775 + 9997776.

It is an arithmetic number, because the mean of its divisors is an integer number (9997776).

Almost surely, 2^19995551 is an apocalyptic number.

19995551 is a deficient number, since it is larger than the sum of its proper divisors (1).

19995551 is an equidigital number, since it uses as much as digits as its factorization.

19995551 is an evil number, because the sum of its binary digits is even.

The product of its digits is 91125, while the sum is 44.

The square root of 19995551 is about 4471.6385140125. The cubic root of 19995551 is about 271.4216327602.

The spelling of 19995551 in words is "nineteen million, nine hundred ninety-five thousand, five hundred fifty-one".