1978691 has 16 divisors (see below), whose sum is σ = 2364768. Its totient is φ = 1632000.

The previous prime is 1978687. The next prime is 1978693. The reversal of 1978691 is 1968791.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 1978691 - 2² = 1978687 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1978693) 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, 14375 + ... + 14511.

It is an arithmetic number, because the mean of its divisors is an integer number (147798).

2^1978691 is an apocalyptic number.

1978691 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

1978691 is a deficient number, since it is larger than the sum of its proper divisors (386077).

1978691 is a wasteful number, since it uses less digits than its factorization.

1978691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 262.

The product of its digits is 27216, while the sum is 41.

The square root of 1978691 is about 1406.6595181493. The cubic root of 1978691 is about 125.5430453972.

It can be divided in two parts, 197 and 8691, that added together give a palindrome (8888).

The spelling of 1978691 in words is "one million, nine hundred seventy-eight thousand, six hundred ninety-one".