661501491 has 16 divisors (see below), whose sum is σ = 1018397184. Its totient is φ = 374102784.

The previous prime is 661501487. The next prime is 661501531. The reversal of 661501491 is 194105166.

It is not a de Polignac number, because 661501491 - 2² = 661501487 is a prime.

It is not an unprimeable number, because it can be changed into a prime (661501411) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 160335 + ... + 164408.

It is an arithmetic number, because the mean of its divisors is an integer number (63649824).

Almost surely, 2^661501491 is an apocalyptic number.

661501491 is a deficient number, since it is larger than the sum of its proper divisors (356895693).

661501491 is a wasteful number, since it uses less digits than its factorization.

661501491 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 324850.

The product of its (nonzero) digits is 6480, while the sum is 33.

The square root of 661501491 is about 25719.6712848357. The cubic root of 661501491 is about 871.3185146750.

The spelling of 661501491 in words is "six hundred sixty-one million, five hundred one thousand, four hundred ninety-one".