19991651 has 2 divisors, whose sum is σ = 19991652. Its totient is φ = 19991650.

The previous prime is 19991639. The next prime is 19991717. The reversal of 19991651 is 15619991.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-19991651 is a prime.

It is a super-2 number, since 2×19991651² = 799332219411602, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 19991599 and 19991608.

It is not a weakly prime, because it can be changed into another prime (19991611) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9995825 + 9995826.

It is an arithmetic number, because the mean of its divisors is an integer number (9995826).

Almost surely, 2^19991651 is an apocalyptic number.

19991651 is a deficient number, since it is larger than the sum of its proper divisors (1).

19991651 is an equidigital number, since it uses as much as digits as its factorization.

19991651 is an evil number, because the sum of its binary digits is even.

The product of its digits is 21870, while the sum is 41.

The square root of 19991651 is about 4471.2024109852. The cubic root of 19991651 is about 271.4039852813.

The spelling of 19991651 in words is "nineteen million, nine hundred ninety-one thousand, six hundred fifty-one".