21979151 has 2 divisors, whose sum is σ = 21979152. Its totient is φ = 21979150.

The previous prime is 21979121. The next prime is 21979159. The reversal of 21979151 is 15197912.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21979151 - 2¹⁴ = 21962767 is a prime.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21979159) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10989575 + 10989576.

It is an arithmetic number, because the mean of its divisors is an integer number (10989576).

Almost surely, 2^21979151 is an apocalyptic number.

21979151 is a deficient number, since it is larger than the sum of its proper divisors (1).

21979151 is an equidigital number, since it uses as much as digits as its factorization.

21979151 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5670, while the sum is 35.

The square root of 21979151 is about 4688.1927221478. The cubic root of 21979151 is about 280.1153903653.

The spelling of 21979151 in words is "twenty-one million, nine hundred seventy-nine thousand, one hundred fifty-one".