21445861 has 2 divisors, whose sum is σ = 21445862. Its totient is φ = 21445860.

The previous prime is 21445847. The next prime is 21445871. The reversal of 21445861 is 16854412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13549761 + 7896100 = 3681^2 + 2810^2 .

It is a cyclic number.

It is not a de Polignac number, because 21445861 - 2⁹ = 21445349 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21445871) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10722930 + 10722931.

It is an arithmetic number, because the mean of its divisors is an integer number (10722931).

Almost surely, 2^21445861 is an apocalyptic number.

It is an amenable number.

21445861 is a deficient number, since it is larger than the sum of its proper divisors (1).

21445861 is an equidigital number, since it uses as much as digits as its factorization.

21445861 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7680, while the sum is 31.

The square root of 21445861 is about 4630.9676094743. The cubic root of 21445861 is about 277.8312943940.

The spelling of 21445861 in words is "twenty-one million, four hundred forty-five thousand, eight hundred sixty-one".