21320406 has 24 divisors (see below), whose sum is σ = 46674264. Its totient is φ = 7032960.

The previous prime is 21320401. The next prime is 21320407. The reversal of 21320406 is 60402312.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21320401) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 4360 + ... + 7851.

It is an arithmetic number, because the mean of its divisors is an integer number (1944761).

Almost surely, 2^21320406 is an apocalyptic number.

21320406 is an abundant number, since it is smaller than the sum of its proper divisors (25353858).

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

21320406 is a wasteful number, since it uses less digits than its factorization.

21320406 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12316 (or 12313 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 18.

The square root of 21320406 is about 4617.4025165671. The cubic root of 21320406 is about 277.2884777189.

Adding to 21320406 its reverse (60402312), we get a palindrome (81722718).

The spelling of 21320406 in words is "twenty-one million, three hundred twenty thousand, four hundred six".