21198974437 has 4 divisors (see below), whose sum is σ = 21716022636. Its totient is φ = 20681926240.

The previous prime is 21198974429. The next prime is 21198974441. The reversal of 21198974437 is 73447989112.

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

It can be written as a sum of positive squares in 2 ways, for example, as 5369811841 + 15829162596 = 73279^2 + 125814^2 .

It is a cyclic number.

It is not a de Polignac number, because 21198974437 - 2³ = 21198974429 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21198954437) 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, 258524038 + ... + 258524119.

It is an arithmetic number, because the mean of its divisors is an integer number (5429005659).

Almost surely, 2^21198974437 is an apocalyptic number.

It is an amenable number.

21198974437 is a deficient number, since it is larger than the sum of its proper divisors (517048199).

21198974437 is an equidigital number, since it uses as much as digits as its factorization.

21198974437 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 517048198.

The product of its digits is 3048192, while the sum is 55.

The spelling of 21198974437 in words is "twenty-one billion, one hundred ninety-eight million, nine hundred seventy-four thousand, four hundred thirty-seven".