21278877 has 8 divisors (see below), whose sum is σ = 29064000. Its totient is φ = 13839840.

The previous prime is 21278861. The next prime is 21278899. The reversal of 21278877 is 77887212.

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

It is not a de Polignac number, because 21278877 - 2⁴ = 21278861 is a prime.

It is a super-2 number, since 2×21278877² = 905581212762258, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21278177) 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 7 ways as a sum of consecutive naturals, for example, 86377 + ... + 86622.

It is an arithmetic number, because the mean of its divisors is an integer number (3633000).

Almost surely, 2^21278877 is an apocalyptic number.

It is an amenable number.

21278877 is a deficient number, since it is larger than the sum of its proper divisors (7785123).

21278877 is a wasteful number, since it uses less digits than its factorization.

21278877 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 173043.

The product of its digits is 87808, while the sum is 42.

The square root of 21278877 is about 4612.9033157004. The cubic root of 21278877 is about 277.1083217042.

It can be divided in two parts, 21278 and 877, that added together give a triangular number (22155 = T₂₁₀).

The spelling of 21278877 in words is "twenty-one million, two hundred seventy-eight thousand, eight hundred seventy-seven".