81503621 has 2 divisors, whose sum is σ = 81503622. Its totient is φ = 81503620.

The previous prime is 81503581. The next prime is 81503641. The reversal of 81503621 is 12630518.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 65383396 + 16120225 = 8086^2 + 4015^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81503621 is a prime.

It is a super-2 number, since 2×81503621² = 13285680472223282, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81503641) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40751810 + 40751811.

It is an arithmetic number, because the mean of its divisors is an integer number (40751811).

Almost surely, 2^81503621 is an apocalyptic number.

It is an amenable number.

81503621 is a deficient number, since it is larger than the sum of its proper divisors (1).

81503621 is an equidigital number, since it uses as much as digits as its factorization.

81503621 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1440, while the sum is 26.

The square root of 81503621 is about 9027.9355890480. The cubic root of 81503621 is about 433.5697439123.

The spelling of 81503621 in words is "eighty-one million, five hundred three thousand, six hundred twenty-one".