21529997 has 2 divisors, whose sum is σ = 21529998. Its totient is φ = 21529996.

The previous prime is 21529979. The next prime is 21530017. The reversal of 21529997 is 79992512.

It is a happy number.

Together with previous prime (21529979) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19061956 + 2468041 = 4366^2 + 1571^2 .

It is a cyclic number.

It is not a de Polignac number, because 21529997 - 2⁸ = 21529741 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21529927) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10764998 + 10764999.

It is an arithmetic number, because the mean of its divisors is an integer number (10764999).

Almost surely, 2^21529997 is an apocalyptic number.

It is an amenable number.

21529997 is a deficient number, since it is larger than the sum of its proper divisors (1).

21529997 is an equidigital number, since it uses as much as digits as its factorization.

21529997 is an evil number, because the sum of its binary digits is even.

The product of its digits is 102060, while the sum is 44.

The square root of 21529997 is about 4640.0427799752. The cubic root of 21529997 is about 278.1941478030.

The spelling of 21529997 in words is "twenty-one million, five hundred twenty-nine thousand, nine hundred ninety-seven".