21015464 has 8 divisors (see below), whose sum is σ = 39404010. Its totient is φ = 10507728.

The previous prime is 21015461. The next prime is 21015473. The reversal of 21015464 is 46451012.

It can be written as a sum of positive squares in only one way, i.e., 20775364 + 240100 = 4558^2 + 490^2 .

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

It is not an unprimeable number, because it can be changed into a prime (21015461) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1313459 + ... + 1313474.

Almost surely, 2^21015464 is an apocalyptic number.

It is an amenable number.

21015464 is a deficient number, since it is larger than the sum of its proper divisors (18388546).

21015464 is a wasteful number, since it uses less digits than its factorization.

21015464 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2626939 (or 2626935 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 23.

The square root of 21015464 is about 4584.2626451808. The cubic root of 21015464 is about 275.9601216626.

Adding to 21015464 its reverse (46451012), we get a palindrome (67466476).

The spelling of 21015464 in words is "twenty-one million, fifteen thousand, four hundred sixty-four".