21026778 has 16 divisors (see below), whose sum is σ = 42182400. Its totient is φ = 6987456.

The previous prime is 21026777. The next prime is 21026779. The reversal of 21026778 is 87762012.

It is an interprime number because it is at equal distance from previous prime (21026777) and next prime (21026779).

It is a super-2 number, since 2×21026778² = 884250786122568, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21026777) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3178 + ... + 7221.

It is an arithmetic number, because the mean of its divisors is an integer number (2636400).

Almost surely, 2^21026778 is an apocalyptic number.

21026778 is an abundant number, since it is smaller than the sum of its proper divisors (21155622).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21026778 is a wasteful number, since it uses less digits than its factorization.

21026778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10741.

The product of its (nonzero) digits is 9408, while the sum is 33.

The square root of 21026778 is about 4585.4964834792. The cubic root of 21026778 is about 276.0096352444.

The spelling of 21026778 in words is "twenty-one million, twenty-six thousand, seven hundred seventy-eight".