1978781 has 4 divisors (see below), whose sum is σ = 2261472. Its totient is φ = 1696092.

The previous prime is 1978771. The next prime is 1978799. The reversal of 1978781 is 1878791.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1978781 - 2¹⁰ = 1977757 is a prime.

It is a super-2 number, since 2×1978781² = 7831148491922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1978741) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 141335 + ... + 141348.

It is an arithmetic number, because the mean of its divisors is an integer number (565368).

2^1978781 is an apocalyptic number.

It is an amenable number.

1978781 is a deficient number, since it is larger than the sum of its proper divisors (282691).

1978781 is an equidigital number, since it uses as much as digits as its factorization.

1978781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 282690.

The product of its digits is 28224, while the sum is 41.

The square root of 1978781 is about 1406.6915084694. The cubic root of 1978781 is about 125.5449487941.

The spelling of 1978781 in words is "one million, nine hundred seventy-eight thousand, seven hundred eighty-one".