21231577 has 2 divisors, whose sum is σ = 21231578. Its totient is φ = 21231576.

The previous prime is 21231557. The next prime is 21231583. The reversal of 21231577 is 77513212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20985561 + 246016 = 4581^2 + 496^2 .

It is a cyclic number.

It is not a de Polignac number, because 21231577 - 2⁷ = 21231449 is a prime.

It is not a weakly prime, because it can be changed into another prime (21231547) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10615788 + 10615789.

It is an arithmetic number, because the mean of its divisors is an integer number (10615789).

Almost surely, 2^21231577 is an apocalyptic number.

It is an amenable number.

21231577 is a deficient number, since it is larger than the sum of its proper divisors (1).

21231577 is an equidigital number, since it uses as much as digits as its factorization.

21231577 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2940, while the sum is 28.

The square root of 21231577 is about 4607.7735404423. The cubic root of 21231577 is about 276.9028448914.

Adding to 21231577 its reverse (77513212), we get a palindrome (98744789).

The spelling of 21231577 in words is "twenty-one million, two hundred thirty-one thousand, five hundred seventy-seven".