1555421665 has 16 divisors (see below), whose sum is σ = 2134016640. Its totient is φ = 1066141440.

The previous prime is 1555421663. The next prime is 1555421669. The reversal of 1555421665 is 5661245551.

It is not a de Polignac number, because 1555421665 - 2¹ = 1555421663 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1555421663) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 95305 + ... + 110425.

It is an arithmetic number, because the mean of its divisors is an integer number (133376040).

Almost surely, 2^1555421665 is an apocalyptic number.

It is an amenable number.

1555421665 is a deficient number, since it is larger than the sum of its proper divisors (578594975).

1555421665 is a wasteful number, since it uses less digits than its factorization.

1555421665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18072.

The product of its digits is 180000, while the sum is 40.

The square root of 1555421665 is about 39438.8344782145. The cubic root of 1555421665 is about 1158.6423039746.

The spelling of 1555421665 in words is "one billion, five hundred fifty-five million, four hundred twenty-one thousand, six hundred sixty-five".