1666666625 has 16 divisors (see below), whose sum is σ = 2240002128. Its totient is φ = 1230768000.

The previous prime is 1666666613. The next prime is 1666666637. The reversal of 1666666625 is 5266666661.

It is an interprime number because it is at equal distance from previous prime (1666666613) and next prime (1666666637).

It can be written as a sum of positive squares in 8 ways, for example, as 1279993729 + 386672896 = 35777^2 + 19664^2 .

It is not a de Polignac number, because 1666666625 - 2¹⁶ = 1666601089 is a prime.

It is a super-4 number, since 4×1666666625⁴ (a number of 38 digits) contains 4444 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 511196 + ... + 514445.

It is an arithmetic number, because the mean of its divisors is an integer number (140000133).

Almost surely, 2^1666666625 is an apocalyptic number.

It is an amenable number.

1666666625 is a deficient number, since it is larger than the sum of its proper divisors (573335503).

1666666625 is a wasteful number, since it uses less digits than its factorization.

1666666625 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1025669 (or 1025659 counting only the distinct ones).

The product of its digits is 2799360, while the sum is 50.

The square root of 1666666625 is about 40824.8285360759. The cubic root of 1666666625 is about 1185.6310916164.

The spelling of 1666666625 in words is "one billion, six hundred sixty-six million, six hundred sixty-six thousand, six hundred twenty-five".