1997778 has 16 divisors (see below), whose sum is σ = 4104000. Its totient is φ = 647856.

The previous prime is 1997773. The next prime is 1997813. The reversal of 1997778 is 8777991.

It is a super-2 number, since 2×1997778² = 7982233874568, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1997771) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4278 + ... + 4721.

It is an arithmetic number, because the mean of its divisors is an integer number (256500).

2^1997778 is an apocalyptic number.

1997778 is an abundant number, since it is smaller than the sum of its proper divisors (2106222).

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

1997778 is a wasteful number, since it uses less digits than its factorization.

1997778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9041.

The product of its digits is 222264, while the sum is 48.

The square root of 1997778 is about 1413.4277484187. The cubic root of 1997778 is about 125.9454286232.

It can be divided in two parts, 1997 and 778, that added together give a triangular number (2775 = T₇₄).

The spelling of 1997778 in words is "one million, nine hundred ninety-seven thousand, seven hundred seventy-eight".