21503997 has 12 divisors (see below), whose sum is σ = 32888700. Its totient is φ = 13492608.

The previous prime is 21503981. The next prime is 21504017. The reversal of 21503997 is 79930512.

It can be written as a sum of positive squares in 2 ways, for example, as 9036036 + 12467961 = 3006^2 + 3531^2 .

It is not a de Polignac number, because 21503997 - 2⁴ = 21503981 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21503917) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 70122 + ... + 70427.

It is an arithmetic number, because the mean of its divisors is an integer number (2740725).

Almost surely, 2^21503997 is an apocalyptic number.

It is an amenable number.

21503997 is a deficient number, since it is larger than the sum of its proper divisors (11384703).

21503997 is a wasteful number, since it uses less digits than its factorization.

21503997 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 140572 (or 140569 counting only the distinct ones).

The product of its (nonzero) digits is 17010, while the sum is 36.

The square root of 21503997 is about 4637.2402353124. The cubic root of 21503997 is about 278.0821186593.

It can be divided in two parts, 21503 and 997, that added together give a square (22500 = 150²).

The spelling of 21503997 in words is "twenty-one million, five hundred three thousand, nine hundred ninety-seven".