18953721 has 6 divisors (see below), whose sum is σ = 27377610. Its totient is φ = 12635808.

The previous prime is 18953719. The next prime is 18953723. The reversal of 18953721 is 12735981.

It is an interprime number because it is at equal distance from previous prime (18953719) and next prime (18953723).

It can be written as a sum of positive squares in only one way, i.e., 17943696 + 1010025 = 4236^2 + 1005^2 .

It is not a de Polignac number, because 18953721 - 2¹ = 18953719 is a prime.

It is not an unprimeable number, because it can be changed into a prime (18953723) 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 5 ways as a sum of consecutive naturals, for example, 1052976 + ... + 1052993.

It is an arithmetic number, because the mean of its divisors is an integer number (4562935).

Almost surely, 2^18953721 is an apocalyptic number.

It is an amenable number.

18953721 is a deficient number, since it is larger than the sum of its proper divisors (8423889).

18953721 is a wasteful number, since it uses less digits than its factorization.

18953721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2105975 (or 2105972 counting only the distinct ones).

The product of its digits is 15120, while the sum is 36.

The square root of 18953721 is about 4353.5871416569. The cubic root of 18953721 is about 266.6233379255.

The spelling of 18953721 in words is "eighteen million, nine hundred fifty-three thousand, seven hundred twenty-one".