715821 has 16 divisors (see below), whose sum is σ = 1013760. Its totient is φ = 448560.

The previous prime is 715817. The next prime is 715823. The reversal of 715821 is 128517.

It is not a de Polignac number, because 715821 - 2² = 715817 is a prime.

715821 is a lucky number.

It is a junction number, because it is equal to n+sod(n) for n = 715791 and 715800.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 715821.

It is not an unprimeable number, because it can be changed into a prime (715823) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3910 + ... + 4088.

It is an arithmetic number, because the mean of its divisors is an integer number (63360).

715821 is a Friedman number, since it can be written as 71^(8-5)*2-1, using all its digits and the basic arithmetic operations.

2⁷¹⁵⁸²¹ is an apocalyptic number.

It is an amenable number.

715821 is a deficient number, since it is larger than the sum of its proper divisors (297939).

715821 is a wasteful number, since it uses less digits than its factorization.

715821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 256.

The product of its digits is 560, while the sum is 24.

The square root of 715821 is about 846.0620544617. The cubic root of 715821 is about 89.4543528867.

The spelling of 715821 in words is "seven hundred fifteen thousand, eight hundred twenty-one".