19999987 has 8 divisors (see below), whose sum is σ = 23324000. Its totient is φ = 17142552.

The previous prime is 19999981. The next prime is 19999999. The reversal of 19999987 is 78999991.

It is not a de Polignac number, because 19999987 - 2¹⁹ = 19475699 is a prime.

It is not an unprimeable number, because it can be changed into a prime (19999981) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 28812 + ... + 29497.

It is an arithmetic number, because the mean of its divisors is an integer number (2915500).

Almost surely, 2^19999987 is an apocalyptic number.

19999987 is a deficient number, since it is larger than the sum of its proper divisors (3324013).

19999987 is an frugal number, since it uses more digits than its factorization.

19999987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 58330 (or 58316 counting only the distinct ones).

The product of its digits is 3306744, while the sum is 61.

The square root of 19999987 is about 4472.1345015552. The cubic root of 19999987 is about 271.4417028471.

It can be divided in two parts, 1999998 and 7, that multiplied together give a triangular number (13999986 = T₅₂₉₁).

The spelling of 19999987 in words is "nineteen million, nine hundred ninety-nine thousand, nine hundred eighty-seven".