21690525 has 24 divisors (see below), whose sum is σ = 36140544. Its totient is φ = 11478400.

The previous prime is 21690523. The next prime is 21690527. The reversal of 21690525 is 52509612.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21690523) and next prime (21690527).

It is not a de Polignac number, because 21690525 - 2¹ = 21690523 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a junction number, because it is equal to n+sod(n) for n = 21690492 and 21690501.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21690523) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 9220 + ... + 11330.

It is an arithmetic number, because the mean of its divisors is an integer number (1505856).

Almost surely, 2^21690525 is an apocalyptic number.

21690525 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21690525 is a deficient number, since it is larger than the sum of its proper divisors (14450019).

21690525 is a wasteful number, since it uses less digits than its factorization.

21690525 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2261 (or 2256 counting only the distinct ones).

The product of its (nonzero) digits is 5400, while the sum is 30.

The square root of 21690525 is about 4657.3087722418. The cubic root of 21690525 is about 278.8838431693.

The spelling of 21690525 in words is "twenty-one million, six hundred ninety thousand, five hundred twenty-five".