21019864 has 8 divisors (see below), whose sum is σ = 39412260. Its totient is φ = 10509928.

The previous prime is 21019849. The next prime is 21019879. The reversal of 21019864 is 46891012.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21019849) and next prime (21019879).

It is a tau number, because it is divible by the number of its divisors (8).

It is a congruent number.

It is an unprimeable number.

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 as a sum of consecutive naturals, namely, 1313734 + ... + 1313749.

Almost surely, 2^21019864 is an apocalyptic number.

It is an amenable number.

21019864 is a deficient number, since it is larger than the sum of its proper divisors (18392396).

21019864 is a wasteful number, since it uses less digits than its factorization.

21019864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2627489 (or 2627485 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 31.

The square root of 21019864 is about 4584.7425227596. The cubic root of 21019864 is about 275.9793795419.

The spelling of 21019864 in words is "twenty-one million, nineteen thousand, eight hundred sixty-four".