21388946 has 32 divisors (see below), whose sum is σ = 35512320. Its totient is φ = 9622800.

The previous prime is 21388943. The next prime is 21388949. The reversal of 21388946 is 64988312.

It is an interprime number because it is at equal distance from previous prime (21388943) and next prime (21388949).

It is not an unprimeable number, because it can be changed into a prime (21388943) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 78791 + ... + 79061.

It is an arithmetic number, because the mean of its divisors is an integer number (1109760).

Almost surely, 2^21388946 is an apocalyptic number.

21388946 is a deficient number, since it is larger than the sum of its proper divisors (14123374).

21388946 is a wasteful number, since it uses less digits than its factorization.

21388946 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 390.

The product of its digits is 82944, while the sum is 41.

The square root of 21388946 is about 4624.8184829245. The cubic root of 21388946 is about 277.5852985623.

The spelling of 21388946 in words is "twenty-one million, three hundred eighty-eight thousand, nine hundred forty-six".