18947421 has 6 divisors (see below), whose sum is σ = 27368510. Its totient is φ = 12631608.

The previous prime is 18947419. The next prime is 18947429. The reversal of 18947421 is 12474981.

18947421 is a `hidden beast` number, since 189 + 474 + 2 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 14907321 + 4040100 = 3861^2 + 2010^2 .

It is not a de Polignac number, because 18947421 - 2¹ = 18947419 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18947429) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1052626 + ... + 1052643.

Almost surely, 2^18947421 is an apocalyptic number.

It is an amenable number.

18947421 is a deficient number, since it is larger than the sum of its proper divisors (8421089).

18947421 is a wasteful number, since it uses less digits than its factorization.

18947421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2105275 (or 2105272 counting only the distinct ones).

The product of its digits is 16128, while the sum is 36.

The square root of 18947421 is about 4352.8635402457. The cubic root of 18947421 is about 266.5937938029.

The spelling of 18947421 in words is "eighteen million, nine hundred forty-seven thousand, four hundred twenty-one".