1097821 has 4 divisors (see below), whose sum is σ = 1102144. Its totient is φ = 1093500.

The previous prime is 1097819. The next prime is 1097849. The reversal of 1097821 is 1287901.

1097821 = T₈₅₄ + T₈₅₅ + T₈₅₆.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 1287901 = 1117 ⋅1153.

It is a 3-Lehmer number, since φ(1097821) divides (1097821-1)³.

It is a cyclic number.

It is not a de Polignac number, because 1097821 - 2¹ = 1097819 is a prime.

It is a Duffinian number.

1097821 is a lucky number.

It is a self number, because there is not a number n which added to its sum of digits gives 1097821.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1097851) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1755 + ... + 2296.

It is an arithmetic number, because the mean of its divisors is an integer number (275536).

2^1097821 is an apocalyptic number.

1097821 is the 856-th centered triangular number.

It is an amenable number.

1097821 is a deficient number, since it is larger than the sum of its proper divisors (4323).

1097821 is an equidigital number, since it uses as much as digits as its factorization.

1097821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4322.

The product of its (nonzero) digits is 1008, while the sum is 28.

The square root of 1097821 is about 1047.7695357282. The cubic root of 1097821 is about 103.1598047198.

The spelling of 1097821 in words is "one million, ninety-seven thousand, eight hundred twenty-one".