21609713 has 2 divisors, whose sum is σ = 21609714. Its totient is φ = 21609712.

The previous prime is 21609701. The next prime is 21609733. The reversal of 21609713 is 31790612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13897984 + 7711729 = 3728^2 + 2777^2 .

It is a cyclic number.

It is not a de Polignac number, because 21609713 - 2⁶ = 21609649 is a prime.

It is not a weakly prime, because it can be changed into another prime (21609733) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10804856 + 10804857.

It is an arithmetic number, because the mean of its divisors is an integer number (10804857).

Almost surely, 2^21609713 is an apocalyptic number.

It is an amenable number.

21609713 is a deficient number, since it is larger than the sum of its proper divisors (1).

21609713 is an equidigital number, since it uses as much as digits as its factorization.

21609713 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2268, while the sum is 29.

The square root of 21609713 is about 4648.6248504262. The cubic root of 21609713 is about 278.5370679763.

It can be divided in two parts, 21609 and 713, that added together give a palindrome (22322).

The spelling of 21609713 in words is "twenty-one million, six hundred nine thousand, seven hundred thirteen".