21309778 has 8 divisors (see below), whose sum is σ = 36531072. Its totient is φ = 9132756.

The previous prime is 21309733. The next prime is 21309787. The reversal of 21309778 is 87790312.

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

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 761050 + ... + 761077.

It is an arithmetic number, because the mean of its divisors is an integer number (4566384).

Almost surely, 2^21309778 is an apocalyptic number.

21309778 is a deficient number, since it is larger than the sum of its proper divisors (15221294).

21309778 is a wasteful number, since it uses less digits than its factorization.

21309778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1522136.

The product of its (nonzero) digits is 21168, while the sum is 37.

The square root of 21309778 is about 4616.2515096125. The cubic root of 21309778 is about 277.2423949228.

The spelling of 21309778 in words is "twenty-one million, three hundred nine thousand, seven hundred seventy-eight".