18721601 has 2 divisors, whose sum is σ = 18721602. Its totient is φ = 18721600.

The previous prime is 18721537. The next prime is 18721627. The reversal of 18721601 is 10612781.

It is an a-pointer prime, because the next prime (18721627) can be obtained adding 18721601 to its sum of digits (26).

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18447025 + 274576 = 4295^2 + 524^2 .

It is a cyclic number.

It is not a de Polignac number, because 18721601 - 2⁶ = 18721537 is a prime.

It is not a weakly prime, because it can be changed into another prime (18720601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9360800 + 9360801.

It is an arithmetic number, because the mean of its divisors is an integer number (9360801).

Almost surely, 2^18721601 is an apocalyptic number.

It is an amenable number.

18721601 is a deficient number, since it is larger than the sum of its proper divisors (1).

18721601 is an equidigital number, since it uses as much as digits as its factorization.

18721601 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 672, while the sum is 26.

The square root of 18721601 is about 4326.8465422291. The cubic root of 18721601 is about 265.5304481189.

The spelling of 18721601 in words is "eighteen million, seven hundred twenty-one thousand, six hundred one".