21278855 has 16 divisors (see below), whose sum is σ = 27597024. Its totient is φ = 15657600.

The previous prime is 21278821. The next prime is 21278861. The reversal of 21278855 is 55887212.

It is a happy number.

It is not a de Polignac number, because 21278855 - 2¹⁰ = 21277831 is a prime.

It is a super-2 number, since 2×21278855² = 905579340222050, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 30005 + ... + 30705.

It is an arithmetic number, because the mean of its divisors is an integer number (1724814).

Almost surely, 2^21278855 is an apocalyptic number.

21278855 is a deficient number, since it is larger than the sum of its proper divisors (6318169).

21278855 is a wasteful number, since it uses less digits than its factorization.

21278855 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1186.

The product of its digits is 44800, while the sum is 38.

The square root of 21278855 is about 4612.9009310845. The cubic root of 21278855 is about 277.1082262044.

The spelling of 21278855 in words is "twenty-one million, two hundred seventy-eight thousand, eight hundred fifty-five".