18817421 has 6 divisors (see below), whose sum is σ = 21889710. Its totient is φ = 16129176.

The previous prime is 18817417. The next prime is 18817439. The reversal of 18817421 is 12471881.

It can be written as a sum of positive squares in only one way, i.e., 11055625 + 7761796 = 3325^2 + 2786^2 .

It is not a de Polignac number, because 18817421 - 2² = 18817417 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 (18817481) 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, 191966 + ... + 192063.

It is an arithmetic number, because the mean of its divisors is an integer number (3648285).

Almost surely, 2^18817421 is an apocalyptic number.

It is an amenable number.

18817421 is a deficient number, since it is larger than the sum of its proper divisors (3072289).

18817421 is an equidigital number, since it uses as much as digits as its factorization.

18817421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 384043 (or 384036 counting only the distinct ones).

The product of its digits is 3584, while the sum is 32.

The square root of 18817421 is about 4337.9051395806. The cubic root of 18817421 is about 265.9826858536.

The spelling of 18817421 in words is "eighteen million, eight hundred seventeen thousand, four hundred twenty-one".