21064861 has 4 divisors (see below), whose sum is σ = 21078972. Its totient is φ = 21050752.

The previous prime is 21064843. The next prime is 21064891. The reversal of 21064861 is 16846012.

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 14485636 + 6579225 = 3806^2 + 2565^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21064861 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21064891) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4510 + ... + 7903.

It is an arithmetic number, because the mean of its divisors is an integer number (5269743).

Almost surely, 2^21064861 is an apocalyptic number.

It is an amenable number.

21064861 is a deficient number, since it is larger than the sum of its proper divisors (14111).

21064861 is a wasteful number, since it uses less digits than its factorization.

21064861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14110.

The product of its (nonzero) digits is 2304, while the sum is 28.

The square root of 21064861 is about 4589.6471541939. The cubic root of 21064861 is about 276.1761678982.

The spelling of 21064861 in words is "twenty-one million, sixty-four thousand, eight hundred sixty-one".