18991625 has 16 divisors (see below), whose sum is σ = 23896080. Its totient is φ = 15068800.

The previous prime is 18991589. The next prime is 18991627. The reversal of 18991625 is 52619981.

It is a happy number.

It can be written as a sum of positive squares in 8 ways, for example, as 11478544 + 7513081 = 3388^2 + 2741^2 .

It is not a de Polignac number, because 18991625 - 2¹⁸ = 18729481 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (18991627) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 16571 + ... + 17679.

It is an arithmetic number, because the mean of its divisors is an integer number (1493505).

Almost surely, 2^18991625 is an apocalyptic number.

It is an amenable number.

18991625 is a deficient number, since it is larger than the sum of its proper divisors (4904455).

18991625 is a wasteful number, since it uses less digits than its factorization.

18991625 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1261 (or 1251 counting only the distinct ones).

The product of its digits is 38880, while the sum is 41.

The square root of 18991625 is about 4357.9381592675. The cubic root of 18991625 is about 266.8009523315.

The spelling of 18991625 in words is "eighteen million, nine hundred ninety-one thousand, six hundred twenty-five".