21439501 has 2 divisors, whose sum is σ = 21439502. Its totient is φ = 21439500.

The previous prime is 21439493. The next prime is 21439513. The reversal of 21439501 is 10593412.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21436900 + 2601 = 4630^2 + 51^2 .

It is a cyclic number.

It is not a de Polignac number, because 21439501 - 2³ = 21439493 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21439571) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10719750 + 10719751.

It is an arithmetic number, because the mean of its divisors is an integer number (10719751).

Almost surely, 2^21439501 is an apocalyptic number.

It is an amenable number.

21439501 is a deficient number, since it is larger than the sum of its proper divisors (1).

21439501 is an equidigital number, since it uses as much as digits as its factorization.

21439501 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1080, while the sum is 25.

The square root of 21439501 is about 4630.2808770095. The cubic root of 21439501 is about 277.8038270623.

The spelling of 21439501 in words is "twenty-one million, four hundred thirty-nine thousand, five hundred one".