101521991 has 2 divisors, whose sum is σ = 101521992. Its totient is φ = 101521990.

The previous prime is 101521963. The next prime is 101522051. The reversal of 101521991 is 199125101.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-101521991 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 (101521961) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 50760995 + 50760996.

It is an arithmetic number, because the mean of its divisors is an integer number (50760996).

Almost surely, 2^101521991 is an apocalyptic number.

101521991 is a deficient number, since it is larger than the sum of its proper divisors (1).

101521991 is an equidigital number, since it uses as much as digits as its factorization.

101521991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 810, while the sum is 29.

The square root of 101521991 is about 10075.8121757008. The cubic root of 101521991 is about 466.5018554631.

The spelling of 101521991 in words is "one hundred one million, five hundred twenty-one thousand, nine hundred ninety-one".