21032543978 has 4 divisors (see below), whose sum is σ = 31548815970. Its totient is φ = 10516271988.

The previous prime is 21032543977. The next prime is 21032544037. The reversal of 21032543978 is 87934523012.

It is a happy number.

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

It can be written as a sum of positive squares in only one way, i.e., 15708360889 + 5324183089 = 125333^2 + 72967^2 .

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21032543977) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5258135993 + ... + 5258135996.

Almost surely, 2^21032543978 is an apocalyptic number.

21032543978 is a deficient number, since it is larger than the sum of its proper divisors (10516271992).

21032543978 is a wasteful number, since it uses less digits than its factorization.

21032543978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10516271991.

The product of its (nonzero) digits is 362880, while the sum is 44.

The spelling of 21032543978 in words is "twenty-one billion, thirty-two million, five hundred forty-three thousand, nine hundred seventy-eight".