1251666555 has 32 divisors (see below), whose sum is σ = 2092317696. Its totient is φ = 637743744.

The previous prime is 1251666527. The next prime is 1251666583. The reversal of 1251666555 is 5556661521.

It is an interprime number because it is at equal distance from previous prime (1251666527) and next prime (1251666583).

It is not a de Polignac number, because 1251666555 - 2⁹ = 1251666043 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 365029 + ... + 368441.

It is an arithmetic number, because the mean of its divisors is an integer number (65384928).

Almost surely, 2^1251666555 is an apocalyptic number.

1251666555 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

1251666555 is a deficient number, since it is larger than the sum of its proper divisors (840651141).

1251666555 is a wasteful number, since it uses less digits than its factorization.

1251666555 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4507.

The product of its digits is 270000, while the sum is 42.

The square root of 1251666555 is about 35378.8998557050. The cubic root of 1251666555 is about 1077.6958636055.

The spelling of 1251666555 in words is "one billion, two hundred fifty-one million, six hundred sixty-six thousand, five hundred fifty-five".