661684225 has 12 divisors (see below), whose sum is σ = 821890476. Its totient is φ = 528442880.

The previous prime is 661684211. The next prime is 661684241. The reversal of 661684225 is 522486166.

It can be written as a sum of positive squares in 6 ways, for example, as 11587216 + 650097009 = 3404^2 + 25497^2 .

It is not a de Polignac number, because 661684225 - 2²⁹ = 124813313 is a prime.

It is a super-2 number, since 2×661684225² = 875652027227701250, which contains 22 as substring.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 7492 + ... + 37141.

It is an arithmetic number, because the mean of its divisors is an integer number (68490873).

It is a Proth number, since it is equal to 20193 ⋅ 2¹⁵ + 1 and 20193 < 2¹⁵.

Almost surely, 2^661684225 is an apocalyptic number.

It is an amenable number.

661684225 is a deficient number, since it is larger than the sum of its proper divisors (160206251).

661684225 is a wasteful number, since it uses less digits than its factorization.

661684225 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 45236 (or 45231 counting only the distinct ones).

The product of its digits is 138240, while the sum is 40.

The square root of 661684225 is about 25723.2234566354. The cubic root of 661684225 is about 871.3987386608.

The spelling of 661684225 in words is "six hundred sixty-one million, six hundred eighty-four thousand, two hundred twenty-five".