90870821 has 2 divisors, whose sum is σ = 90870822. Its totient is φ = 90870820.

The previous prime is 90870817. The next prime is 90870839. The reversal of 90870821 is 12807809.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 89397025 + 1473796 = 9455^2 + 1214^2 .

It is a cyclic number.

It is not a de Polignac number, because 90870821 - 2² = 90870817 is a prime.

It is a super-2 number, since 2×90870821² = 16515012218428082, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (90870851) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45435410 + 45435411.

It is an arithmetic number, because the mean of its divisors is an integer number (45435411).

Almost surely, 2^90870821 is an apocalyptic number.

It is an amenable number.

90870821 is a deficient number, since it is larger than the sum of its proper divisors (1).

90870821 is an equidigital number, since it uses as much as digits as its factorization.

90870821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 8064, while the sum is 35.

The square root of 90870821 is about 9532.6187902381. The cubic root of 90870821 is about 449.5812087279.

The spelling of 90870821 in words is "ninety million, eight hundred seventy thousand, eight hundred twenty-one".