21019978402 has 8 divisors (see below), whose sum is σ = 31531434012. Its totient is φ = 10509500400.

The previous prime is 21019978387. The next prime is 21019978403. The reversal of 21019978402 is 20487991012.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 16592273721 + 4427704681 = 128811^2 + 66541^2 .

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

It is not an unprimeable number, because it can be changed into a prime (21019978403) by changing a digit.

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 in 3 ways as a sum of consecutive naturals, for example, 188049 + ... + 278212.

Almost surely, 2^21019978402 is an apocalyptic number.

21019978402 is a deficient number, since it is larger than the sum of its proper divisors (10511455610).

21019978402 is a wasteful number, since it uses less digits than its factorization.

21019978402 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 488804.

The product of its (nonzero) digits is 72576, while the sum is 43.

The spelling of 21019978402 in words is "twenty-one billion, nineteen million, nine hundred seventy-eight thousand, four hundred two".