21502997 has 2 divisors, whose sum is σ = 21502998. Its totient is φ = 21502996.

The previous prime is 21502993. The next prime is 21503033. The reversal of 21502997 is 79920512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21104836 + 398161 = 4594^2 + 631^2 .

It is a cyclic number.

It is not a de Polignac number, because 21502997 - 2² = 21502993 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21502993) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10751498 + 10751499.

It is an arithmetic number, because the mean of its divisors is an integer number (10751499).

Almost surely, 2^21502997 is an apocalyptic number.

It is an amenable number.

21502997 is a deficient number, since it is larger than the sum of its proper divisors (1).

21502997 is an equidigital number, since it uses as much as digits as its factorization.

21502997 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 11340, while the sum is 35.

The square root of 21502997 is about 4637.1324113077. The cubic root of 21502997 is about 278.0778080431.

The spelling of 21502997 in words is "twenty-one million, five hundred two thousand, nine hundred ninety-seven".