21278026 has 32 divisors (see below), whose sum is σ = 40030848. Its totient is φ = 8240640.

The previous prime is 21278021. The next prime is 21278041. The reversal of 21278026 is 62087212.

21278026 is a nontrivial binomial coefficient, being equal to C(6524, 2).

It is a junction number, because it is equal to n+sod(n) for n = 21277985 and 21278003.

It is not an unprimeable number, because it can be changed into a prime (21278021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 35586 + ... + 36178.

It is an arithmetic number, because the mean of its divisors is an integer number (1250964).

Almost surely, 2^21278026 is an apocalyptic number.

21278026 is the 6523-rd triangular number and also the 3262-nd hexagonal number.

21278026 is the 2175-th centered nonagonal number.

21278026 is a deficient number, since it is larger than the sum of its proper divisors (18752822).

21278026 is a wasteful number, since it uses less digits than its factorization.

21278026 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 846.

The product of its (nonzero) digits is 2688, while the sum is 28.

The square root of 21278026 is about 4612.8110735212. The cubic root of 21278026 is about 277.1046275505.

It can be divided in two parts, 2127 and 8026, that added together give a triangular number (10153 = T₁₄₂).

The spelling of 21278026 in words is "twenty-one million, two hundred seventy-eight thousand, twenty-six".