21531619 has 2 divisors, whose sum is σ = 21531620. Its totient is φ = 21531618.

The previous prime is 21531599. The next prime is 21531623. The reversal of 21531619 is 91613512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21531619 - 2⁷ = 21531491 is a prime.

It is a super-2 number, since 2×21531619² = 927221233522322, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21531649) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10765809 + 10765810.

It is an arithmetic number, because the mean of its divisors is an integer number (10765810).

Almost surely, 2^21531619 is an apocalyptic number.

21531619 is a deficient number, since it is larger than the sum of its proper divisors (1).

21531619 is an equidigital number, since it uses as much as digits as its factorization.

21531619 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1620, while the sum is 28.

The square root of 21531619 is about 4640.2175595547. The cubic root of 21531619 is about 278.2011337085.

The spelling of 21531619 in words is "twenty-one million, five hundred thirty-one thousand, six hundred nineteen".