91021551 has 8 divisors (see below), whose sum is σ = 122289024. Its totient is φ = 60217560.

The previous prime is 91021543. The next prime is 91021559. The reversal of 91021551 is 15512019.

It is an interprime number because it is at equal distance from previous prime (91021543) and next prime (91021559).

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 91021551 - 2³ = 91021543 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91021559) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 115411 + ... + 116196.

It is an arithmetic number, because the mean of its divisors is an integer number (15286128).

Almost surely, 2^91021551 is an apocalyptic number.

91021551 is a deficient number, since it is larger than the sum of its proper divisors (31267473).

91021551 is a wasteful number, since it uses less digits than its factorization.

91021551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 231741.

The product of its (nonzero) digits is 450, while the sum is 24.

The square root of 91021551 is about 9540.5215266253. The cubic root of 91021551 is about 449.8296491008.

The spelling of 91021551 in words is "ninety-one million, twenty-one thousand, five hundred fifty-one".