1821997538 has 4 divisors (see below), whose sum is σ = 2732996310. Its totient is φ = 910998768.

The previous prime is 1821997523. The next prime is 1821997553. The reversal of 1821997538 is 8357991281.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (1821997523) and next prime (1821997553).

It can be written as a sum of positive squares in only one way, i.e., 1299097849 + 522899689 = 36043^2 + 22867^2 .

It is a super-2 number, since 2×1821997538² = 6639350056956122888, which contains 22 as substring.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 1821997538.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 455499383 + ... + 455499386.

Almost surely, 2^1821997538 is an apocalyptic number.

1821997538 is a deficient number, since it is larger than the sum of its proper divisors (910998772).

1821997538 is an equidigital number, since it uses as much as digits as its factorization.

1821997538 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 910998771.

The product of its digits is 1088640, while the sum is 53.

The square root of 1821997538 is about 42684.8631015727. The cubic root of 1821997538 is about 1221.3756626887.

The spelling of 1821997538 in words is "one billion, eight hundred twenty-one million, nine hundred ninety-seven thousand, five hundred thirty-eight".