1981716421 has 6 divisors (see below), whose sum is σ = 2052408722. Its totient is φ = 1913380560.

The previous prime is 1981716403. The next prime is 1981716433. The reversal of 1981716421 is 1246171891.

It can be written as a sum of positive squares in 3 ways, for example, as 71064900 + 1910651521 = 8430^2 + 43711^2 .

It is not a de Polignac number, because 1981716421 - 2⁵ = 1981716389 is a prime.

It is a super-2 number, since 2×1981716421² = 7854399946522098482, 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 (1981716461) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1177350 + ... + 1179031.

Almost surely, 2^1981716421 is an apocalyptic number.

It is an amenable number.

1981716421 is a deficient number, since it is larger than the sum of its proper divisors (70692301).

1981716421 is an equidigital number, since it uses as much as digits as its factorization.

1981716421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2356439 (or 2356410 counting only the distinct ones).

The product of its digits is 24192, while the sum is 40.

The square root of 1981716421 is about 44516.4735912448. The cubic root of 1981716421 is about 1256.0699797125.

The spelling of 1981716421 in words is "one billion, nine hundred eighty-one million, seven hundred sixteen thousand, four hundred twenty-one".