1781490021 has 12 divisors (see below), whose sum is σ = 2426943072. Its totient is φ = 1162386328.

The previous prime is 1781489999. The next prime is 1781490059. The reversal of 1781490021 is 1200941871.

It is not a de Polignac number, because 1781490021 - 2²⁶ = 1714381157 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1781490071) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 127785 + ... + 141038.

It is an arithmetic number, because the mean of its divisors is an integer number (202245256).

Almost surely, 2^1781490021 is an apocalyptic number.

It is an amenable number.

1781490021 is a deficient number, since it is larger than the sum of its proper divisors (645453051).

1781490021 is an equidigital number, since it uses as much as digits as its factorization.

1781490021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 268920 (or 268873 counting only the distinct ones).

The product of its (nonzero) digits is 4032, while the sum is 33.

The square root of 1781490021 is about 42207.7009679513. The cubic root of 1781490021 is about 1212.2563415302.

The spelling of 1781490021 in words is "one billion, seven hundred eighty-one million, four hundred ninety thousand, twenty-one".