18690021 has 60 divisors (see below), whose sum is σ = 34512588. Its totient is φ = 10015488.

The previous prime is 18690019. The next prime is 18690029. The reversal of 18690021 is 12009681.

It can be written as a sum of positive squares in 2 ways, for example, as 8767521 + 9922500 = 2961^2 + 3150^2 .

It is not a de Polignac number, because 18690021 - 2¹ = 18690019 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18690029) by changing a digit.

It is a polite number, since it can be written in 59 ways as a sum of consecutive naturals, for example, 67335 + ... + 67611.

Almost surely, 2^18690021 is an apocalyptic number.

It is an amenable number.

18690021 is a deficient number, since it is larger than the sum of its proper divisors (15822567).

18690021 is a wasteful number, since it uses less digits than its factorization.

18690021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 320 (or 304 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 27.

The square root of 18690021 is about 4323.1956930030. The cubic root of 18690021 is about 265.3810632649.

The spelling of 18690021 in words is "eighteen million, six hundred ninety thousand, twenty-one".