21951511 has 2 divisors, whose sum is σ = 21951512. Its totient is φ = 21951510.

The previous prime is 21951497. The next prime is 21951529. The reversal of 21951511 is 11515912.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21951511 - 2⁷ = 21951383 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21951551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10975755 + 10975756.

It is an arithmetic number, because the mean of its divisors is an integer number (10975756).

Almost surely, 2^21951511 is an apocalyptic number.

21951511 is a deficient number, since it is larger than the sum of its proper divisors (1).

21951511 is an equidigital number, since it uses as much as digits as its factorization.

21951511 is an evil number, because the sum of its binary digits is even.

The product of its digits is 450, while the sum is 25.

The square root of 21951511 is about 4685.2439637654. The cubic root of 21951511 is about 279.9979209029.

The spelling of 21951511 in words is "twenty-one million, nine hundred fifty-one thousand, five hundred eleven".