21859973 has 2 divisors, whose sum is σ = 21859974. Its totient is φ = 21859972.

The previous prime is 21859949. The next prime is 21859979. The reversal of 21859973 is 37995812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18645124 + 3214849 = 4318^2 + 1793^2 .

It is a cyclic number.

It is not a de Polignac number, because 21859973 - 2¹² = 21855877 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21859979) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10929986 + 10929987.

It is an arithmetic number, because the mean of its divisors is an integer number (10929987).

Almost surely, 2^21859973 is an apocalyptic number.

It is an amenable number.

21859973 is a deficient number, since it is larger than the sum of its proper divisors (1).

21859973 is an equidigital number, since it uses as much as digits as its factorization.

21859973 is an evil number, because the sum of its binary digits is even.

The product of its digits is 136080, while the sum is 44.

The square root of 21859973 is about 4675.4650036119. The cubic root of 21859973 is about 279.6081807031.

The spelling of 21859973 in words is "twenty-one million, eight hundred fifty-nine thousand, nine hundred seventy-three".