1661617678 has 32 divisors (see below), whose sum is σ = 3039517440. Its totient is φ = 665392320.

The previous prime is 1661617673. The next prime is 1661617693. The reversal of 1661617678 is 8767161661.

It is a super-2 number, since 2×1661617678² = 5521946615684223368, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1661617673) 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, 23368 + ... + 62203.

It is an arithmetic number, because the mean of its divisors is an integer number (94984920).

Almost surely, 2^1661617678 is an apocalyptic number.

1661617678 is a deficient number, since it is larger than the sum of its proper divisors (1377899762).

1661617678 is a wasteful number, since it uses less digits than its factorization.

1661617678 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 85672.

The product of its digits is 508032, while the sum is 49.

The square root of 1661617678 is about 40762.9449132420. The cubic root of 1661617678 is about 1184.4326428811.

The spelling of 1661617678 in words is "one billion, six hundred sixty-one million, six hundred seventeen thousand, six hundred seventy-eight".