684545721 has 32 divisors (see below), whose sum is σ = 953188992. Its totient is φ = 436700160.

The previous prime is 684545713. The next prime is 684545731. The reversal of 684545721 is 127545486.

It is a happy number.

It is not a de Polignac number, because 684545721 - 2³ = 684545713 is a prime.

It is not an unprimeable number, because it can be changed into a prime (684545731) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1580721 + ... + 1581153.

It is an arithmetic number, because the mean of its divisors is an integer number (29787156).

Almost surely, 2^684545721 is an apocalyptic number.

684545721 is a gapful number since it is divisible by the number (61) formed by its first and last digit.

It is an amenable number.

684545721 is a deficient number, since it is larger than the sum of its proper divisors (268643271).

684545721 is a wasteful number, since it uses less digits than its factorization.

684545721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 713.

The product of its digits is 268800, while the sum is 42.

The square root of 684545721 is about 26163.8246630725. The cubic root of 684545721 is about 881.3210706325.

The spelling of 684545721 in words is "six hundred eighty-four million, five hundred forty-five thousand, seven hundred twenty-one".