21402739 has 2 divisors, whose sum is σ = 21402740. Its totient is φ = 21402738.

The previous prime is 21402713. The next prime is 21402763. The reversal of 21402739 is 93720412.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21402739 - 2¹⁷ = 21271667 is a prime.

It is not a weakly prime, because it can be changed into another prime (21402239) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10701369 + 10701370.

It is an arithmetic number, because the mean of its divisors is an integer number (10701370).

Almost surely, 2^21402739 is an apocalyptic number.

21402739 is a deficient number, since it is larger than the sum of its proper divisors (1).

21402739 is an equidigital number, since it uses as much as digits as its factorization.

21402739 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3024, while the sum is 28.

The square root of 21402739 is about 4626.3094362569. The cubic root of 21402739 is about 277.6449541637.

The spelling of 21402739 in words is "twenty-one million, four hundred two thousand, seven hundred thirty-nine".