21396740 has 24 divisors (see below), whose sum is σ = 45050712. Its totient is φ = 8536320.

The previous prime is 21396733. The next prime is 21396743. The reversal of 21396740 is 4769312.

It can be written as a sum of positive squares in 4 ways, for example, as 6895876 + 14500864 = 2626^2 + 3808^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21396697 and 21396706.

It is not an unprimeable number, because it can be changed into a prime (21396743) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7970 + ... + 10310.

It is an arithmetic number, because the mean of its divisors is an integer number (1877113).

Almost surely, 2^21396740 is an apocalyptic number.

21396740 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21396740 is an abundant number, since it is smaller than the sum of its proper divisors (23653972).

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

21396740 is a wasteful number, since it uses less digits than its factorization.

21396740 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2807 (or 2805 counting only the distinct ones).

The product of its (nonzero) digits is 9072, while the sum is 32.

The square root of 21396740 is about 4625.6610338415. The cubic root of 21396740 is about 277.6190112580.

The spelling of 21396740 in words is "twenty-one million, three hundred ninety-six thousand, seven hundred forty".