21001029278 has 4 divisors (see below), whose sum is σ = 31501543920. Its totient is φ = 10500514638.

The previous prime is 21001029277. The next prime is 21001029311. The reversal of 21001029278 is 87292010012.

It is a happy number.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001029277) 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 as a sum of consecutive naturals, namely, 5250257318 + ... + 5250257321.

It is an arithmetic number, because the mean of its divisors is an integer number (7875385980).

Almost surely, 2^21001029278 is an apocalyptic number.

21001029278 is a deficient number, since it is larger than the sum of its proper divisors (10500514642).

21001029278 is a wasteful number, since it uses less digits than its factorization.

21001029278 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10500514641.

The product of its (nonzero) digits is 4032, while the sum is 32.

The spelling of 21001029278 in words is "twenty-one billion, one million, twenty-nine thousand, two hundred seventy-eight".