1997981 has 4 divisors (see below), whose sum is σ = 2062464. Its totient is φ = 1933500.

The previous prime is 1997969. The next prime is 1997999. The reversal of 1997981 is 1897991.

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 1997981 - 2¹⁴ = 1981597 is a prime.

It is a super-2 number, since 2×1997981² = 7983856152722, 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 (1997911) 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, 32195 + ... + 32256.

It is an arithmetic number, because the mean of its divisors is an integer number (515616).

2^1997981 is an apocalyptic number.

It is an amenable number.

1997981 is a deficient number, since it is larger than the sum of its proper divisors (64483).

1997981 is an equidigital number, since it uses as much as digits as its factorization.

1997981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 64482.

The product of its digits is 40824, while the sum is 44.

The square root of 1997981 is about 1413.4995578351. The cubic root of 1997981 is about 125.9496943718.

The spelling of 1997981 in words is "one million, nine hundred ninety-seven thousand, nine hundred eighty-one".