21195778 has 16 divisors (see below), whose sum is σ = 32607360. Its totient is φ = 10328656.

The previous prime is 21195767. The next prime is 21195791. The reversal of 21195778 is 87759112.

It is a super-2 number, since 2×21195778² = 898522010050568, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21195778.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 41388 + ... + 41896.

It is an arithmetic number, because the mean of its divisors is an integer number (2037960).

Almost surely, 2^21195778 is an apocalyptic number.

21195778 is a deficient number, since it is larger than the sum of its proper divisors (11411582).

21195778 is a wasteful number, since it uses less digits than its factorization.

21195778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1001.

The product of its digits is 35280, while the sum is 40.

The square root of 21195778 is about 4603.8872705573. The cubic root of 21195778 is about 276.7471268056.

The spelling of 21195778 in words is "twenty-one million, one hundred ninety-five thousand, seven hundred seventy-eight".