21420664 has 8 divisors (see below), whose sum is σ = 40163760. Its totient is φ = 10710328.

The previous prime is 21420661. The next prime is 21420667. The reversal of 21420664 is 46602412.

It is an interprime number because it is at equal distance from previous prime (21420661) and next prime (21420667).

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21420661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1338784 + ... + 1338799.

It is an arithmetic number, because the mean of its divisors is an integer number (5020470).

Almost surely, 2^21420664 is an apocalyptic number.

It is an amenable number.

21420664 is a deficient number, since it is larger than the sum of its proper divisors (18743096).

21420664 is a wasteful number, since it uses less digits than its factorization.

21420664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2677589 (or 2677585 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 25.

The square root of 21420664 is about 4628.2463201519. The cubic root of 21420664 is about 277.7224426428.

The spelling of 21420664 in words is "twenty-one million, four hundred twenty thousand, six hundred sixty-four".