821649 has 8 divisors (see below), whose sum is σ = 1099872. Its totient is φ = 545600.

The previous prime is 821647. The next prime is 821651. The reversal of 821649 is 946128.

It is an interprime number because it is at equal distance from previous prime (821647) and next prime (821651).

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 821649 - 2¹ = 821647 is a prime.

821649 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (821641) 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, 862 + ... + 1544.

It is an arithmetic number, because the mean of its divisors is an integer number (137484).

2⁸²¹⁶⁴⁹ is an apocalyptic number.

It is an amenable number.

821649 is a deficient number, since it is larger than the sum of its proper divisors (278223).

821649 is a wasteful number, since it uses less digits than its factorization.

821649 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1087.

The product of its digits is 3456, while the sum is 30.

The square root of 821649 is about 906.4485644536. The cubic root of 821649 is about 93.6617160005.

The spelling of 821649 in words is "eight hundred twenty-one thousand, six hundred forty-nine".