21901465 has 4 divisors (see below), whose sum is σ = 26281764. Its totient is φ = 17521168.

The previous prime is 21901463. The next prime is 21901489. The reversal of 21901465 is 56410912.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 2996361 + 18905104 = 1731^2 + 4348^2 .

It is a cyclic number.

It is not a de Polignac number, because 21901465 - 2¹ = 21901463 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21901463) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2190142 + ... + 2190151.

It is an arithmetic number, because the mean of its divisors is an integer number (6570441).

Almost surely, 2^21901465 is an apocalyptic number.

It is an amenable number.

21901465 is a deficient number, since it is larger than the sum of its proper divisors (4380299).

21901465 is an equidigital number, since it uses as much as digits as its factorization.

21901465 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4380298.

The product of its (nonzero) digits is 2160, while the sum is 28.

The square root of 21901465 is about 4679.9001057715. The cubic root of 21901465 is about 279.7849752211.

It can be divided in two parts, 21901 and 465, that added together give a triangular number (22366 = T₂₁₁).

The spelling of 21901465 in words is "twenty-one million, nine hundred one thousand, four hundred sixty-five".