21723797 has 2 divisors, whose sum is σ = 21723798. Its totient is φ = 21723796.

The previous prime is 21723791. The next prime is 21723853. The reversal of 21723797 is 79732712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16313521 + 5410276 = 4039^2 + 2326^2 .

It is a cyclic number.

It is not a de Polignac number, because 21723797 - 2⁶ = 21723733 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21723797.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21723791) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10861898 + 10861899.

It is an arithmetic number, because the mean of its divisors is an integer number (10861899).

Almost surely, 2^21723797 is an apocalyptic number.

It is an amenable number.

21723797 is a deficient number, since it is larger than the sum of its proper divisors (1).

21723797 is an equidigital number, since it uses as much as digits as its factorization.

21723797 is an evil number, because the sum of its binary digits is even.

The product of its digits is 37044, while the sum is 38.

The square root of 21723797 is about 4660.8794234565. The cubic root of 21723797 is about 279.0263675015.

The spelling of 21723797 in words is "twenty-one million, seven hundred twenty-three thousand, seven hundred ninety-seven".