21513511 has 2 divisors, whose sum is σ = 21513512. Its totient is φ = 21513510.

The previous prime is 21513469. The next prime is 21513523. The reversal of 21513511 is 11531512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21513511 - 2⁷ = 21513383 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21517511) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10756755 + 10756756.

It is an arithmetic number, because the mean of its divisors is an integer number (10756756).

Almost surely, 2^21513511 is an apocalyptic number.

21513511 is a deficient number, since it is larger than the sum of its proper divisors (1).

21513511 is an equidigital number, since it uses as much as digits as its factorization.

21513511 is an evil number, because the sum of its binary digits is even.

The product of its digits is 150, while the sum is 19.

The square root of 21513511 is about 4638.2659475282. The cubic root of 21513511 is about 278.1231231789.

The spelling of 21513511 in words is "twenty-one million, five hundred thirteen thousand, five hundred eleven".