21077778 has 8 divisors (see below), whose sum is σ = 42155568. Its totient is φ = 7025924.

The previous prime is 21077759. The next prime is 21077779. The reversal of 21077778 is 87777012.

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

21077778 is an admirable number.

It is not an unprimeable number, because it can be changed into a prime (21077779) 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 3 ways as a sum of consecutive naturals, for example, 1756476 + ... + 1756487.

It is an arithmetic number, because the mean of its divisors is an integer number (5269446).

Almost surely, 2^21077778 is an apocalyptic number.

21077778 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21077778 is a wasteful number, since it uses less digits than its factorization.

21077778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3512968.

The product of its (nonzero) digits is 38416, while the sum is 39.

The square root of 21077778 is about 4591.0541273220. The cubic root of 21077778 is about 276.2326068914.

The spelling of 21077778 in words is "twenty-one million, seventy-seven thousand, seven hundred seventy-eight".