18821261 has 8 divisors (see below), whose sum is σ = 20616120. Its totient is φ = 17102848.

The previous prime is 18821239. The next prime is 18821279. The reversal of 18821261 is 16212881.

It can be written as a sum of positive squares in 4 ways, for example, as 1223236 + 17598025 = 1106^2 + 4195^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 18821261 - 2²² = 14626957 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (29).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18821161) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 18596 + ... + 19581.

It is an arithmetic number, because the mean of its divisors is an integer number (2577015).

Almost surely, 2^18821261 is an apocalyptic number.

It is an amenable number.

18821261 is a deficient number, since it is larger than the sum of its proper divisors (1794859).

18821261 is a wasteful number, since it uses less digits than its factorization.

18821261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 38223.

The product of its digits is 1536, while the sum is 29.

The square root of 18821261 is about 4338.3477269578. The cubic root of 18821261 is about 266.0007773170. Note that the first 3 decimals are identical.

The spelling of 18821261 in words is "eighteen million, eight hundred twenty-one thousand, two hundred sixty-one".