21739747 has 2 divisors, whose sum is σ = 21739748. Its totient is φ = 21739746.

The previous prime is 21739741. The next prime is 21739759. The reversal of 21739747 is 74793712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21739747 - 2¹¹ = 21737699 is a prime.

It is not a weakly prime, because it can be changed into another prime (21739741) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10869873 + 10869874.

It is an arithmetic number, because the mean of its divisors is an integer number (10869874).

Almost surely, 2^21739747 is an apocalyptic number.

21739747 is a deficient number, since it is larger than the sum of its proper divisors (1).

21739747 is an equidigital number, since it uses as much as digits as its factorization.

21739747 is an evil number, because the sum of its binary digits is even.

The product of its digits is 74088, while the sum is 40.

The square root of 21739747 is about 4662.5901599862. The cubic root of 21739747 is about 279.0946395107.

The spelling of 21739747 in words is "twenty-one million, seven hundred thirty-nine thousand, seven hundred forty-seven".