21778394 has 16 divisors (see below), whose sum is σ = 37734336. Its totient is φ = 9316800.

The previous prime is 21778387. The next prime is 21778409. The reversal of 21778394 is 49387712.

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, 28742 + ... + 29489.

It is an arithmetic number, because the mean of its divisors is an integer number (2358396).

Almost surely, 2^21778394 is an apocalyptic number.

21778394 is a deficient number, since it is larger than the sum of its proper divisors (15955942).

21778394 is a wasteful number, since it uses less digits than its factorization.

21778394 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 58261.

The product of its digits is 84672, while the sum is 41.

The square root of 21778394 is about 4666.7326900091. The cubic root of 21778394 is about 279.2599248637.

The spelling of 21778394 in words is "twenty-one million, seven hundred seventy-eight thousand, three hundred ninety-four".