21513125 has 10 divisors (see below), whose sum is σ = 26883582. Its totient is φ = 17210000.

The previous prime is 21513113. The next prime is 21513127. The reversal of 21513125 is 52131512.

It is a happy number.

It can be written as a sum of positive squares in 5 ways, for example, as 2660161 + 18852964 = 1631^2 + 4342^2 .

It is not a de Polignac number, because 21513125 - 2⁶ = 21513061 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21513097 and 21513106.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21513127) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 16586 + ... + 17835.

Almost surely, 2^21513125 is an apocalyptic number.

21513125 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21513125 is a deficient number, since it is larger than the sum of its proper divisors (5370457).

21513125 is an frugal number, since it uses more digits than its factorization.

21513125 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 34441 (or 34426 counting only the distinct ones).

The product of its digits is 300, while the sum is 20.

The square root of 21513125 is about 4638.2243369634. The cubic root of 21513125 is about 278.1214597875.

Adding to 21513125 its reverse (52131512), we get a palindrome (73644637).

The spelling of 21513125 in words is "twenty-one million, five hundred thirteen thousand, one hundred twenty-five".