661142621 has 4 divisors (see below), whose sum is σ = 667321632. Its totient is φ = 654963612.

The previous prime is 661142539. The next prime is 661142623. The reversal of 661142621 is 126241166.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 661142621 - 2²⁶ = 594033757 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661142623) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3089345 + ... + 3089558.

It is an arithmetic number, because the mean of its divisors is an integer number (166830408).

Almost surely, 2^661142621 is an apocalyptic number.

It is an amenable number.

661142621 is a deficient number, since it is larger than the sum of its proper divisors (6179011).

661142621 is a wasteful number, since it uses less digits than its factorization.

661142621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6179010.

The product of its digits is 3456, while the sum is 29.

The square root of 661142621 is about 25712.6937717541. The cubic root of 661142621 is about 871.1609203524.

Adding to 661142621 its reverse (126241166), we get a palindrome (787383787).

The spelling of 661142621 in words is "six hundred sixty-one million, one hundred forty-two thousand, six hundred twenty-one".