21688747442 has 8 divisors (see below), whose sum is σ = 32537628396. Its totient is φ = 10842871312.

The previous prime is 21688747429. The next prime is 21688747459. The reversal of 21688747442 is 24474788612.

It is a happy number.

It is a Cunningham number, because it is equal to 147271²+1.

It can be written as a sum of positive squares in 2 ways, for example, as 21688747441 + 1 = 147271^2 + 1^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 733073 + ... + 762084.

Almost surely, 2^21688747442 is an apocalyptic number.

21688747442 is a deficient number, since it is larger than the sum of its proper divisors (10848880954).

21688747442 is a wasteful number, since it uses less digits than its factorization.

21688747442 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1502412.

The product of its digits is 4816896, while the sum is 53.

The spelling of 21688747442 in words is "twenty-one billion, six hundred eighty-eight million, seven hundred forty-seven thousand, four hundred forty-two".