1661205078 has 32 divisors (see below), whose sum is σ = 3975535200. Its totient is φ = 511139808.

The previous prime is 1661205059. The next prime is 1661205101. The reversal of 1661205078 is 8705021661.

1661205078 is digitally balanced in base 4, because in such base it contains all the possibile digits an equal number of times.

It is a super-2 number, since 2×1661205078² = 5519204622345972168, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1182493 + ... + 1183896.

It is an arithmetic number, because the mean of its divisors is an integer number (124235475).

Almost surely, 2^1661205078 is an apocalyptic number.

1661205078 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

1661205078 is an abundant number, since it is smaller than the sum of its proper divisors (2314330122).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1661205078 is a wasteful number, since it uses less digits than its factorization.

1661205078 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2366413 (or 2366407 counting only the distinct ones).

The product of its (nonzero) digits is 20160, while the sum is 36.

The square root of 1661205078 is about 40757.8836300414. The cubic root of 1661205078 is about 1184.3345983930.

The spelling of 1661205078 in words is "one billion, six hundred sixty-one million, two hundred five thousand, seventy-eight".