247821 has 8 divisors (see below), whose sum is σ = 377664. Its totient is φ = 141600.

The previous prime is 247813. The next prime is 247829. The reversal of 247821 is 128742.

It is an interprime number because it is at equal distance from previous prime (247813) and next prime (247829).

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

It is not a de Polignac number, because 247821 - 2³ = 247813 is a prime.

It is a super-2 number, since 2×247821² = 122830496082, which contains 22 as substring.

247821 is a lucky number.

It is a junction number, because it is equal to n+sod(n) for n = 247791 and 247800.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (247829) 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, 5880 + ... + 5921.

It is an arithmetic number, because the mean of its divisors is an integer number (47208).

2²⁴⁷⁸²¹ is an apocalyptic number.

247821 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

247821 is a deficient number, since it is larger than the sum of its proper divisors (129843).

247821 is a wasteful number, since it uses less digits than its factorization.

247821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11811.

The product of its digits is 896, while the sum is 24.

The square root of 247821 is about 497.8162311536. The cubic root of 247821 is about 62.8124936264.

The spelling of 247821 in words is "two hundred forty-seven thousand, eight hundred twenty-one".