1978631 has 2 divisors, whose sum is σ = 1978632. Its totient is φ = 1978630.

The previous prime is 1978597. The next prime is 1978661. The reversal of 1978631 is 1368791.

It is a strong prime.

It is an emirp because it is prime and its reverse (1368791) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1978631 - 2⁶ = 1978567 is a prime.

It is a super-2 number, since 2×1978631² = 7829961268322, which contains 22 as substring.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 1978591 and 1978600.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1978661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 989315 + 989316.

It is an arithmetic number, because the mean of its divisors is an integer number (989316).

2^1978631 is an apocalyptic number.

1978631 is a deficient number, since it is larger than the sum of its proper divisors (1).

1978631 is an equidigital number, since it uses as much as digits as its factorization.

1978631 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9072, while the sum is 35.

The square root of 1978631 is about 1406.6381908650. The cubic root of 1978631 is about 125.5417764339.

The spelling of 1978631 in words is "one million, nine hundred seventy-eight thousand, six hundred thirty-one".