21655001 has 2 divisors, whose sum is σ = 21655002. Its totient is φ = 21655000.

The previous prime is 21654989. The next prime is 21655009. The reversal of 21655001 is 10055612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10896601 + 10758400 = 3301^2 + 3280^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21655001 is a prime.

It is not a weakly prime, because it can be changed into another prime (21655009) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10827500 + 10827501.

It is an arithmetic number, because the mean of its divisors is an integer number (10827501).

Almost surely, 2^21655001 is an apocalyptic number.

It is an amenable number.

21655001 is a deficient number, since it is larger than the sum of its proper divisors (1).

21655001 is an equidigital number, since it uses as much as digits as its factorization.

21655001 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 300, while the sum is 20.

The square root of 21655001 is about 4653.4934189273. The cubic root of 21655001 is about 278.7315111709.

The spelling of 21655001 in words is "twenty-one million, six hundred fifty-five thousand, one".