21478739 has 2 divisors, whose sum is σ = 21478740. Its totient is φ = 21478738.

The previous prime is 21478733. The next prime is 21478741. The reversal of 21478739 is 93787412.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21478739 - 2²⁴ = 4701523 is a prime.

It is a super-2 number, since 2×21478739² = 922672458060242, which contains 22 as substring.

Together with 21478741, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21478696 and 21478705.

It is not a weakly prime, because it can be changed into another prime (21478733) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10739369 + 10739370.

It is an arithmetic number, because the mean of its divisors is an integer number (10739370).

Almost surely, 2^21478739 is an apocalyptic number.

21478739 is a deficient number, since it is larger than the sum of its proper divisors (1).

21478739 is an equidigital number, since it uses as much as digits as its factorization.

21478739 is an odious number, because the sum of its binary digits is odd.

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

The square root of 21478739 is about 4634.5160480896. The cubic root of 21478739 is about 277.9732001493.

It can be divided in two parts, 2 and 1478739, that added together give a palindrome (1478741).

The spelling of 21478739 in words is "twenty-one million, four hundred seventy-eight thousand, seven hundred thirty-nine".