21575531 has 2 divisors, whose sum is σ = 21575532. Its totient is φ = 21575530.

The previous prime is 21575497. The next prime is 21575537. The reversal of 21575531 is 13557512.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21575531 - 2⁶ = 21575467 is a prime.

It is a super-2 number, since 2×21575531² = 931007075863922, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21575494 and 21575503.

It is not a weakly prime, because it can be changed into another prime (21575537) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10787765 + 10787766.

It is an arithmetic number, because the mean of its divisors is an integer number (10787766).

Almost surely, 2^21575531 is an apocalyptic number.

21575531 is a deficient number, since it is larger than the sum of its proper divisors (1).

21575531 is an equidigital number, since it uses as much as digits as its factorization.

21575531 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5250, while the sum is 29.

The square root of 21575531 is about 4644.9468242381. The cubic root of 21575531 is about 278.3901282103.

The spelling of 21575531 in words is "twenty-one million, five hundred seventy-five thousand, five hundred thirty-one".