21519551 has 2 divisors, whose sum is σ = 21519552. Its totient is φ = 21519550.

The previous prime is 21519541. The next prime is 21519557. The reversal of 21519551 is 15591512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21519551 - 2¹⁸ = 21257407 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21519557) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10759775 + 10759776.

It is an arithmetic number, because the mean of its divisors is an integer number (10759776).

Almost surely, 2^21519551 is an apocalyptic number.

21519551 is a deficient number, since it is larger than the sum of its proper divisors (1).

21519551 is an equidigital number, since it uses as much as digits as its factorization.

21519551 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2250, while the sum is 29.

The square root of 21519551 is about 4638.9170072335. The cubic root of 21519551 is about 278.1491487848.

The spelling of 21519551 in words is "twenty-one million, five hundred nineteen thousand, five hundred fifty-one".